  United States Court of Appeals
      for the Federal Circuit
                ______________________

                    WORLDS INC.,
                      Appellant

                           v.

                   BUNGIE, INC.,
                       Appellee
                ______________________

            2017-1481, 2017-1546, 2017-1583
                ______________________

   Appeals from the United States Patent and Trade-
mark Office, Patent Trial and Appeal Board in Nos.
IPR2015-01264, IPR2015-01319, IPR2015-01321.
                ______________________

              Decided: September 7, 2018
                ______________________

    WAYNE MICHAEL HELGE, Davidson Berquist Jackson
& Gowdey, LLP, McLean, VA, argued for appellant. Also
represented by GREGORY A. KRAUSS, ALDO NOTO.

    MICHAEL T. ROSATO, Wilson, Sonsini, Goodrich &
Rosati, PC, Seattle, WA, argued for appellee. Also repre-
sented by MATTHEW A. ARGENTI, Palo Alto, CA; RICHARD
TORCZON, Washington, DC.
                 ______________________

   Before PROST, Chief Judge, O’MALLEY and TARANTO,
                    Circuit Judges.
2                                WORLDS INC.   v. BUNGIE, INC.



PROST, Chief Judge.
     Appellant Worlds Inc. (“Worlds”) appeals the final de-
cisions of the Patent Trial and Appeal Board (“Board”)
invalidating three patents in three inter partes reviews
(“IPRs”). Because we hold that the Board erred in its
real-party-in-interest analysis, we vacate its decisions and
remand for proceedings consistent with this opinion.
                             I
    This consolidated appeal involves three related pa-
tents: U.S. Patent Nos. 7,945,856 (“the ’856 patent”);
8,082,501 (“the ’501 patent”); and 8,145,998 (“the ’998
patent”) (collectively, the “patents-on-appeal”). 1 These
patents generally relate to the computer-generated dis-
play of avatars in a virtual world, including methods and
systems to determine which particular avatars are dis-
played in a given situation.
    In 2012, Worlds asserted the patents-on-appeal,
among other patents, against Activision Publishing, Inc.
(“Activision”) and other related entities in the District of
Massachusetts. J.A. 2992–3002 (Compl.), 4902–04 (Am.
Compl.). Activision develops, publishes, licenses, and
distributes videogames. In the district court litigation
against Activision, Worlds accused certain videogames,
such as Call of Duty, of infringing claims of Worlds’s
patents.
    Appellee Bungie, Inc. (“Bungie”) is an independent
videogame developer that has developed games such as
Halo. Bungie also developed the series of products rele-
vant to these appeals—the Destiny products. Destiny is
developed by Bungie and distributed by Activision.



    1   The case numbers of the IPRs on appeal are:
IPR2015-01264 (the ’856 patent); IPR2015-01319 (the ’501
patent); and IPR2015-01321 (the ’998 patent).
WORLDS INC.   v. BUNGIE, INC.                              3



     Bungie is not a party to the litigation between Worlds
and Activision. In November 2014, however, Worlds
notified Activision that it intended to add Destiny as an
additional accused product in the district court litigation.
J.A. 2944. Approximately six months after Worlds noti-
fied Activision of its intent to add Bungie’s products to the
litigation, Bungie filed six IPR petitions, including the
three IPRs at issue in this case, challenging Worlds’s
patents. 2 These petitions were filed more than one year
after Activision had been served with a complaint alleging
infringement of the patents challenged in the IPR peti-
tions.
    Soon after Bungie filed its IPR petitions, Worlds
moved under 37 C.F.R. § 42.51(b) for routine discovery or,
alternatively, additional discovery, requesting infor-
mation regarding whether Activision should have been
named as a real party in interest to the proceedings, thus
making the petitions time-barred under 35 U.S.C.
§ 315(b). J.A. 394–405. 3 To support its request for dis-
covery, Worlds submitted evidence of a Software Publish-
ing and Development Agreement (“DevPub Agreement”)
between Bungie and Activision. 4
    The DevPub Agreement provides that the Destiny
products would be developed by Bungie and published by
Activision. Under the Agreement, Bungie is responsible
for conducting “legal reviews of the Products to ensure


    2   The case numbers of the IPRs that are not on ap-
peal are: IPR2015-01325 (the ’998 patent); IPR2015-
01268 (U.S. Patent No. 7,181,690); and IPR2015-01269
(U.S. Patent No. 7,493,558). Worlds did not appeal the
final written decisions in these three IPRs.
    3   The same motion was filed in all six pending
IPRs. J.A. 394 n.1.
    4   Worlds discovered the DevPub Agreement
through its own independent investigation. See J.A. 400.
4                               WORLDS INC.   v. BUNGIE, INC.



that all Intellectual Property and other rights are fully
cleared for use.” J.A. 2924. Such “legal reviews” are
“subject to prior review and approval of Activision, (budg-
et to [sic] mutually approved) such approval not to be
unreasonably withheld.” Id. The Agreement also con-
tains certain representations and warranties, as well as
indemnity provisions. J.A. 2933–36. And, the Agreement
contemplates financial support from Activision to Bungie
for development of the Destiny products. J.A. 2928–29.
     Based on the DevPub Agreement, Worlds’s discovery
motion contained six specific requests for production
seeking further details of the relationship between Ac-
tivision and Bungie. J.A. 394–97. Bungie opposed the
motion for discovery, J.A. 407–18, and the Board denied
the motion in its entirety, J.A. 423–32. In doing so, the
Board concluded that Worlds had not shown more than a
“mere allegation” that something useful would have been
found through the requested discovery. J.A. 430.
    Four days later, Worlds filed its pre-institution Pre-
liminary Response, arguing that Bungie should have
named Activision as a real party in interest. J.A. 434–77,
3841–49, 5047–57. In its decisions to institute, the Board
rejected Worlds’s argument, concluding that “Patent
Owner has not demonstrated that Activision is an un-
named real party in interest in this proceeding.” J.A. 511,
3878, 5095.
    The Board issued final written decisions in these
three IPRs on November 10, 2016; November 28, 2016;
and December 6, 2016. In these final decisions, the Board
reiterated its rejection of Worlds’s real-party-in-interest
argument by referring back to the analysis in its institu-
tion decisions. J.A. 106–07, 194–95, 258–59. Finding the
petitions not time-barred, the Board proceeded to address
the patentability of the instituted claims.
WORLDS INC.   v. BUNGIE, INC.                               5



    Worlds timely appealed each final written decision.
We have jurisdiction pursuant to 28 U.S.C.
§ 1295(a)(4)(A).
                                II
     This consolidated appeal presents two issues. First,
Worlds contends that Bungie’s IPR petitions were time-
barred because an alleged real party in interest, Ac-
tivision, had been served with a complaint alleging in-
fringement of these patents over one year prior to the
IPRs’ filing dates. Second, Worlds appeals the Board’s
substantive obviousness analysis.
                                A
     Under 35 U.S.C. § 312(a)(2), an IPR petition “may be
considered only if . . . the petition identifies all real par-
ties in interest.” Correctly identifying all real parties in
interest with respect to each IPR petition is important, as
the determination may impact whether a petition may be
instituted. See 35 U.S.C. § 315(a)(1) (concerning a real
party in interest’s civil action challenging the patent’s
validity); id. § 315(b) (concerning a patent owner’s civil
action against a real party in interest). It may also limit
the arguments available in subsequent proceedings. See
id. § 315(e). In this case, Worlds argues that Bungie’s
IPR petitions were time-barred under § 315(b) because
they were filed over one year after Worlds served Ac-
tivision, the alleged real party in interest, with a com-
plaint alleging infringement of the challenged patents. 5



    5   The parties’ briefing in this case occurred prior to
this court’s en banc decision in Wi-Fi One, LLC v. Broad-
com Corp., 878 F.3d 1364 (Fed. Cir. 2018) (en banc). As
such, Bungie in its briefing relied on Achates Reference
Publishing, Inc. v. Apple Inc. to argue that the Board’s
real-party-in-interest determination for purposes of
6                                WORLDS INC.   v. BUNGIE, INC.



    On appeal, Worlds contends that the Board placed the
burden of persuasion on the patent owner to prove that
Bungie’s petitions were time-barred under § 315(b) be-
cause Activision was a real party in interest, and that this
allocation of the burden was error. These appeals there-
fore require us to determine the appropriate burden
framework for analyzing the real-party-in-interest deter-
minations in these IPRs. Worlds has not sought review of
the Board’s order denying Worlds’s motion for discovery
on this issue.
                             1
    Absent from the Board’s analysis of the real-party-in-
interest issue is any clear statement of what, if any,
burden framework the Board used to analyze the evidence
presented in these IPRs, including an identification of
which party the Board viewed as bearing the burden of
persuasion.
    Both Worlds and Bungie point us to Atlanta Gas Light
Co. v. Bennett Regulator Guards, Inc. as representing a
burden framework used by other Board panels in the real-
party-in-interest analysis. See IPR2013-00453, Paper 88
(P.T.A.B. Jan. 6, 2015). Although there is no indication
that the Board relied on Atlanta Gas Light in these ap-
peals, we find it appropriate to begin our analysis with
that decision, given the parties’ focus on that framework.



evaluating the time bar under § 315(b) is not subject to
review by this court. 803 F.3d 652, 659 (Fed. Cir. 2015),
overruled by Wi-Fi One, 878 F.3d at 1367. In Wi-Fi One,
the court overruled Achates and held that the § 314(d) bar
on the appeal of the Director’s determination of whether
to institute an IPR proceeding does not apply to the
Board’s time-bar determinations under § 315(b), thus
making such time-bar determinations reviewable on
appeal. Wi-Fi One, 878 F.3d at 1367.
WORLDS INC.   v. BUNGIE, INC.                              7



     Under Atlanta Gas Light, the Board generally accepts
an IPR petitioner’s identification of the real parties in
interest at the time the petition is filed. Atlanta Gas
Light, Paper 88 at 7 (citing ZOLL Lifecor Corp. v. Philips
Elec. N. Am. Corp., IPR2013-00606, Paper 13 at 7
(P.T.A.B. Mar. 20, 2014), which cites 77 Fed. Reg. at
48,695). 6 Atlanta Gas Light explained that this initial
acceptance “acts as a rebuttable presumption” that bene-
fits the IPR petitioner. Id. Quoting Federal Rule of
Evidence 301, the Board stated that “[t]he party against
whom a presumption is directed has the burden of produc-
ing evidence to rebut the presumption. But this rule does
not shift the burden of persuasion, which remains on the
party who had it originally.” Id. at 8 (quoting Fed. R.
Evid. 301 (emphasis in Board’s opinion)). From this, the
Board in Atlanta Gas Light explained that, where “a
patent owner provides sufficient rebuttal evidence that
reasonably brings into question the accuracy of a petition-
er’s identification of the real parties in interest, the bur-
den remains with the petitioner to establish that it has
complied with the statutory requirement to identify all
the real parties in interest.” Id.
    We largely concur with the burden framework used in
Atlanta Gas Light. As explained below, we agree that the
IPR petitioner bears the burden of persuasion to demon-
strate that its petitions are not time-barred under
§ 315(b) based on a complaint served on a real party in



    6    The Federal Register notice cited in Atlanta Gas
Light includes the PTO’s responses to public comments.
In response to a question regarding burdens of proof and
persuasion in a challenge to the real-party-in-interest
identification, the PTO stated: “The Office generally will
accept the petitioner’s ‘real party-in-interest’ identifica-
tion at the time of filing the petition.” Part III, 77 Fed.
Reg. 48,680, 48,695 (Aug. 14, 2012).
8                                 WORLDS INC.   v. BUNGIE, INC.



interest more than a year earlier. We also agree that an
IPR petitioner’s initial identification of the real parties in
interest should be accepted unless and until disputed by a
patent owner. And although we disagree with treating
this initial acceptance as a “rebuttable presumption” that
formally shifts a burden of production to the patent
owner, we agree that a patent owner must produce some
evidence to support its argument that a particular third
party should be named a real party in interest.
    At the outset, there can be no doubt that the IPR peti-
tioner bears the ultimate burden of persuasion to show
that its petitions are not time-barred under § 315(b) based
on a complaint served on an alleged real party in interest
more than a year earlier. On this point, the relevant
statute is clear. Under § 556(d) of the Administrative
Procedure Act (“APA”), “[e]xcept as otherwise provided by
statute, the proponent of a rule or order has the burden of
proof.” 5 U.S.C. § 556(d); see also id. § 551(6) (defining
“order” to mean “the whole or a part of a final disposition,
whether affirmative, negative, injunctive, or declaratory
in form, of an agency in a matter other than rule making
but including licensing”). The Supreme Court has ex-
plained that this provision of the APA refers to the bur-
den of persuasion.        Dir., Office of Workers’ Comp.
Programs, Dep’t of Labor v. Greenwich Collieries, 512 U.S.
267, 276 (1994) (“[W]e understand the APA’s unadorned
reference to ‘burden of proof’ to refer to the burden of
persuasion.”). Thus, because the IPR petitioner is the
party seeking an order from the Board, § 556(d) requires
the petitioner to bear the burden of persuasion. And,
while § 556(d) allows for exceptions to be provided by
statute, no such exception exists here.
    This allocation of the burden of persuasion makes
sense. First, it is consistent with the general rule that
“[a]bsent some reason to believe that Congress intended
otherwise, . . . we will conclude that the burden of persua-
sion lies where it usually falls, upon the party seeking
WORLDS INC.   v. BUNGIE, INC.                              9



relief.” Schaffer ex rel. Schaffer v. Weast, 546 U.S. 49, 57–
58 (2005); see also id. at 57 (indicating that § 556(d)
reflects the “general rule” that the party seeking court
action bears the burden of persuasion regarding the
essential aspects of the party’s claims). 7 And as this court
held in Wi-Fi One, “[t]he timely filing of a petition under
§ 315(b) is a condition precedent to the Director’s authori-
ty to act.” 878 F.3d at 1374; see also 35 U.S.C. § 312(a)(2)
(requiring an IPR petitioner to identify all real parties in
interest). Second, an IPR petitioner will usually be in a
better position, at least relative to the patent owner, to
access evidence relevant to the real-party-in-interest
inquiry. See United States v. N.Y., New Haven & Hart-
ford R.R. Co., 355 U.S. 253, 256 n.5 (1957) (“The ordinary
rule, based on considerations of fairness, does not place
the burden upon a litigant of establishing facts peculiarly
within the knowledge of his adversary.”).
    Having identified the party bearing the burden of per-
suasion, we turn to the proper procedure for analyzing
whether a petition should be time-barred based on a
complaint served on a real party in interest more than a
year earlier. As discussed above, the Board in Atlanta
Gas Light explained that its practice of “initially accept-
ing the identification of real parties in interest in a peti-
tion as accurate acts as a rebuttable presumption that



    7   Although exceptions to this general rule exist, for
example, where elements of a plaintiff’s claim “can fairly
be characterized as affirmative defenses or exemptions,”
Schaffer, 546 U.S. at 57, we do not view § 315(b) as an
affirmative defense. Instead, unlike a traditional statute
of limitations defense, “[t]he timely filing of a petition
under § 315(b) is a condition precedent to the Director’s
authority to act,” and “[it] sets limits on the Director’s
statutory authority to institute.” Wi-Fi One, 878 F.3d at
1374.
10                                 WORLDS INC.   v. BUNGIE, INC.



benefits petitioners.” Atlanta Gas Light, Paper 88 at 7.
Referring to Federal Rule of Evidence 301, the Board
indicated that such a presumption shifts the burden of
production to the patent owner, who then must produce
evidence sufficient to “reasonably bring[] into question the
accuracy of a petitioner’s identification of the real parties
in interest.” Id. at 8.
     Initially, we question the Board’s practice of creating
a “presumption” by its acceptance of a petitioner’s initial
identification of the real parties in interest. Generally, for
a party to gain the benefit of a presumption, the party
must prove certain basic facts from which the presumed
fact is then inferred according to the relevant substantive
law. See A.C. Aukerman Co. v. R.L. Chaides Constr. Co.,
960 F.2d 1020, 1035–37 (Fed. Cir. 1992) (en banc) (ex-
plaining that the presumption of laches, which was a
defense available in patent cases prior to SCA Hygiene,
arose upon proof that the patentee delayed filing suit for
more than six years after actual or constructive
knowledge of the defendant’s alleged infringing activi-
ty), abrogated on other grounds by SCA Hygiene Prods.
Aktiebolag v. First Quality Baby Prods., LLC, 137 S. Ct.
954 (2017); 21B Charles A. Wright & Kenneth W. Gra-
ham, Jr., Federal Practice and Procedure: Evidence
§ 5122 (2d ed. 2005) (“[A] true presumption cannot arise
without proof of some ‘basic fact’. . . .”). In the real-party-
in-interest context at issue here, the relevant statute and
regulations do not require evidentiary proof of such basic
facts. See 35 U.S.C. § 312(a)(2) (requiring a petition to
“identif[y] all real parties in interest”); 37 C.F.R.
§ 42.8(b)(1) (requiring a party to “[i]dentify each real
party-in-interest for the party”); see also id. § 42.104(a)
(requiring a petitioner to “certify . . . that the petitioner is
not barred or estopped from requesting an inter partes
review challenging the patent claims on the grounds
identified in the petition”).
WORLDS INC.   v. BUNGIE, INC.                               11



    Moreover, presumptions are usually created based on
certain policy considerations, such as correcting an imbal-
ance due to one party’s superior access to sources of proof,
or promoting efficiency by presuming a fact to be true
where the existence of certain basic facts makes the truth
of the presumed fact highly probable. See 2 George E.
Dix, et al., McCormick on Evidence § 343 (7th ed. 2016).
In the real-party-in-interest context, however, we see no
particular need to create a formal presumption—
especially a presumption that would disfavor the party
that likely has inferior access to potential sources of proof.
    Regardless, we agree that an IPR petitioner’s initial
identification of the real parties in interest should be
accepted unless and until disputed by a patent owner.
But instead of viewing this as a presumption, we simply
view this as practical. In short, we see no reason for the
Board to question an IPR petitioner’s identification of the
real parties in interest unless and until a patent owner
has chosen to raise the issue.
     The next question then becomes: what must a patent
owner do to sufficiently raise the issue? In Atlanta Gas
Light, the Board viewed the “presumption” created by the
IPR petitioner’s initial identification of the real parties in
interest as shifting the burden of production to the patent
owner. From this, the Board explained that, where “a
patent owner provides sufficient rebuttal evidence that
reasonably brings into question the accuracy of a petition-
er’s identification of the real parties in interest, the burden
remains with the petitioner to establish that it has com-
plied with the statutory requirement to identify all the
real parties in interest.” Atlanta Gas Light, Paper 88 at 8
(emphasis added). As explained above, we disagree with
the use of a presumption in this context. We agree,
however, that a patent owner must produce some evidence
that tends to show that a particular third party should be
12                                WORLDS INC.   v. BUNGIE, INC.



named a real party in interest. 8 A mere assertion that a
third party is an unnamed real party in interest, without
any support for that assertion, is insufficient to put the
issue into dispute.
                              2
     In view of this burden framework, we next turn to the
Board’s analysis of the evidence in this case. In its IPR
petitions, Bungie listed itself—and only itself—as the real
party in interest. 9 J.A. 354, 3728, 4918. Worlds then
presented evidence that a particular third party, Ac-
tivision, was an unnamed real party in interest, includ-
ing: (1) the DevPub Agreement between Bungie and
Activision, which related to development of Destiny;
(2) the November 2014 letter indicating Worlds’s intent to
add Bungie’s Destiny products to the Activision litigation;
and (3) the fact that the five patents asserted in the
Activision litigation were the same five patents Bungie
challenged in its IPR petitions.



     8   For purposes of deciding this case, we need not
address the quantum of support required from a patent
owner. If it were not framed in terms of a presumption,
the standard used in Atlantic Gas Light—evidence that
“reasonably brings into question the accuracy of a peti-
tioner’s identification of the real parties in interest”—may
prove useful. In this case, it suffices to say that, as dis-
cussed below, Worlds presented more than enough evi-
dence to sufficiently put this issue into dispute.
    9    Bungie’s identification of the real parties in inter-
est reads, in its entirety: “Bungie, Inc. is the real party-
in-interest.” J.A. 354, 3728, 4918. Given the statutory
requirement that an IPR petition list “all real parties in
interest,” 35 U.S.C. § 312(a)(2) (emphasis added),
Bungie’s statement effectively represents that Bungie is
the sole real party in interest.
WORLDS INC.   v. BUNGIE, INC.                             13



     Worlds focused much of its argument on Recital 7A.15
of the DevPub Agreement, which Worlds views as giving
Activision an opportunity to control the instant IPRs. 10
This provision is found in the section of the DevPub
Agreement titled “Activision’s Responsibilities” and
provides that Bungie is responsible for “[c]onducting legal
reviews of the Products to ensure that all Intellectual
Property and other rights are fully cleared for use.”
J.A. 2924, Recital 7A.15. 11 The section further provides
that these legal reviews “shall be subject to prior review
and approval of Activision, (budget to [sic] mutually
approved) such approval not to be unreasonably with-
held.” Id. From this evidence, Worlds argued before the
Board that these IPRs are “legal reviews” necessary to
clear intellectual property rights, and that Activision had
the opportunity to control the IPRs, making Activision a
real party in interest. In response, Bungie presented a
different interpretation of the “legal reviews” provision,
arguing that, in the context of a videogame development
agreement, a “legal review[]” refers to “reviewing the title,
script, and visual and audio assets to ensure that any
appropriate rights have been obtained and that they do


    10   Worlds also emphasized other portions of the
DevPub Agreement, such as the section regarding Ac-
tivision’s participation in Bungie’s Board of Directors’
meetings, J.A. 2938, Recital 18.2, as well as the section
requiring Activision to pay “development advances” to
Bungie to “fully fund [Bungie’s] operations directly relat-
ed to the development of the Products,” J.A. 2928–29,
Recital 10.1. And it also pointed to representations and
warranties made by Bungie, including that the products
would not violate the rights of others. See J.A. 2933,
Recital 14.1.2.
     11  “Intellectual Property” is defined in the DevPub
Agreement to include patents and patent rights.
J.A. 2919, Recital 6.1.
14                               WORLDS INC.   v. BUNGIE, INC.



not infringe any trademarks or copyrights.”          J.A. 415
(Opp. to Worlds’s Discovery Mot.). 12
    The Board flatly rejected Worlds’s argument that
Bungie’s IPRs could be considered “legal review[s] of a
‘Product,’” first in its order denying Worlds’s discovery
motion, then again in its institution decisions. J.A. 429
(Discovery Order) (stating that “[a] legal review of a
‘Product’ under the Agreement and other provisions do
not specify, require, or necessarily include filing an IPR
against a patent”); J.A. 507, 3874, 5092 (Institution
Decisions) (stating that Worlds’s argument was based on
a faulty assumption that “legal reviews” could include
IPRs). The Board’s institution decisions explained that
the IPRs involved a patent rather than a product, and
thus the IPRs could not be considered “legal reviews of a
Product” that would give Activision a right of review and
approval. J.A. 507 (“The only subject of this proceeding is
the ’856 patent; this proceeding does not involve any
product. Thus, Patent Owner has not shown that this
proceeding falls within the scope of a ‘legal review[] of the
Products’ . . . .” (citation omitted)); see also J.A. 3874,
5092.
    After rejecting each of Worlds’s other arguments re-
garding the DevPub Agreement, the Board concluded that
“Patent Owner has not demonstrated that the Agreement
gives Activision any opportunity to control this proceed-
ing.” J.A. 509, 3877, 5094. In so doing, the Board also
relied on statements in Bungie’s Opposition to Worlds’s
Motion for Discovery, including that “Bungie is solely
responsible for the cost and control of the IPRs against
[Worlds’s] patents,” J.A. 409–10, and that “Activision’s
payment of development advances to Bungie funded the
development of the Destiny videogame, not these IPRs,”


     12  The parties maintain their respective interpreta-
tions of this provision on appeal.
WORLDS INC.   v. BUNGIE, INC.                               15



J.A. 416. See J.A. 510, 3877, 5094–95 (relying on these
statements). In Bungie’s briefing, those statements were
made without citations to any evidence. See J.A. 409–10,
416. Nonetheless, from these statements, the Board
concluded that “Petitioner has expressly denied any
control or funding of this proceeding by Activision,” and
“[o]n this record, we accept Petitioner’s express represen-
tations that Activision is not controlling or funding this
proceeding.” J.A. 509–10, 3877, 5094–95. The Board
ultimately concluded its real-party-in-interest analysis by
stating that “Patent Owner has not demonstrated that
Activision is an unnamed real party in interest in this
proceeding. Accordingly, Patent Owner has not estab-
lished that the Petition violates 35 U.S.C. § 312(a)(2) or
that institution of review is barred under 35 U.S.C.
§ 315(b).” J.A. 511, 3878, 5095. The Board reaffirmed
this analysis in its final written decisions. J.A. 106–07,
194–95, 258–59.
     Under the framework we have outlined above, the
Board was entitled to rely, at least initially, on Bungie’s
list of all real parties in interest, which raised no time-bar
issues under the facts presented. Here, however, Worlds
presented evidence sufficient to put Bungie’s identifica-
tion of itself as the sole real party in interest into dispute.
Thus, in this circumstance, the Board could no longer
merely rely upon Bungie’s initial identification of the real
parties in interest. Instead, the Board was required to
make any factual determinations necessary to evaluate
whether Bungie had satisfied its burden to demonstrate
that its petition was not time-barred based on the com-
plaints served upon Activision, the alleged real party in
interest.
    This marks the point in the analysis at which the
burden of persuasion becomes essential. There is here a
complete absence of any statement as to which party
should bear the burden of persuasion. At the same time,
the Board rejected the patent owner’s arguments because
16                               WORLDS INC.   v. BUNGIE, INC.



the Board was “unpersuaded that there is sufficient
evidence that Activision is an unnamed real party in
interest for the reasons given in the Institution Decision.”
J.A. 107, 195, 259. This implies that the Board assumed
the burden of persuasion rests with the patent owner.
Moreover, the Board’s potential reliance on the rebuttable
presumption from Atlanta Gas Light may have effectively
skewed the burden of persuasion despite Atlanta Gas
Light’s statement that it was not approving such a shift.
Under these circumstances, we cannot discern whether
the Board placed the burden on Worlds, the patent owner,
to persuade the Board that Bungie failed to list a real
party in interest that would render the petitions time-
barred under § 315(b). As discussed above, this would
have been improper.
    As an aside, we have some concern that the Board
may have relied on attorney argument as evidence that
Activision was not controlling or funding these IPRs. See
J.A. 510, 3877, 5095 (citing Bungie’s briefing and stating
that “[o]n this record, we accept Petitioner’s express
representations that Activision is not controlling or fund-
ing this proceeding”); see also Icon Health & Fitness, Inc.
v. Strava, Inc., 849 F.3d 1034, 1043 (Fed. Cir. 2017)
(“Attorney argument is not evidence.”). This is particular-
ly concerning given that the Board’s apparent reliance on
such statements seemed to outweigh the actual evidence
presented by Worlds. Instead of citing evidence to sup-
port this factual conclusion, the Board merely cited attor-
ney argument from Bungie’s briefing—attorney argument
that itself failed to cite evidence, such as affidavits or
declarations. See J.A. 510, 3877, 5095 (Institution Deci-
sions); J.A. 409–10, 416 (Bungie’s briefing).
    In light of these concerns, we find it appropriate to
remand this case to the Board for further consideration of
the real-party-in-interest issue. In doing so, we do not
speak to how the evidence should be weighed, and we do
not prejudge what conclusion the Board, applying a
WORLDS INC.   v. BUNGIE, INC.                           17



proper analysis, may reach as to whether Activision is a
real party in interest in these proceedings. We note,
however, that we have issued opinions since the Board
issued its final written decisions that clarify the meaning
of the term “real party in interest” in the context of
§ 315(b). See Applications in Internet Time, LLC v. RPX
Corp., 897 F.3d 1336, 1351 (Fed. Cir. 2018) (explaining
that determining whether a party is a real party in inter-
est “demands a flexible approach that takes into account
both equitable and practical considerations, with an eye
toward determining whether the non-party is a clear
beneficiary that has a preexisting, established relation-
ship with the petitioner”); Wi-Fi One, LLC v. Broadcom
Corp., 887 F.3d 1329, 1336 (Fed. Cir. 2018) (noting that
the Board, in rendering § 315(b) determinations, “seeks to
determine whether some party other than the petitioner
is the ‘party or parties at whose behest the petition has
been filed’” (citing Office Patent Trial Practice Guide, 77
Fed. Reg. 48,756, 48,759 (Aug. 14, 2012))). We remand
with instructions for the Board to weigh the evidence in a
manner that places the ultimate burden of persuasion on
Bungie, the IPR petitioner, and to do so in a manner
consistent with our recent precedent.
                                3
    Bungie briefly argues on appeal that, in light of issue
preclusion principles, Worlds should be estopped from
contesting the Board’s real-party-in-interest determina-
tion. Bungie bases its preclusion argument on the three
other IPRs that proceeded on a similar time frame as the
three IPRs now on appeal. 13 In those IPRs, Worlds ar-



   13  The Board issued final written decisions in the
three IPRs on appeal on November 10, 2016; November
28, 2016; and December 6, 2016. Meanwhile, the Board
issued final written decisions in the three unappealed
18                               WORLDS INC.   v. BUNGIE, INC.



gued, as it does here, that Bungie should have named
Activision as a real party in interest. The Board disa-
greed. Worlds did not appeal the Board’s final written
decisions in those IPRs, and the time for appeal has now
expired.
     The general rule for issue preclusion (also called col-
lateral estoppel) is “[w]hen an issue of fact or law is
actually litigated and determined by a valid and final
judgment, and the determination is essential to the
judgment, the determination is conclusive in a subsequent
action between the parties, whether on the same or a
different claim.” B & B Hardware, Inc. v. Hargis Indus.,
Inc., 135 S. Ct. 1293, 1303 (2015) (quoting Restatement
(Second) of Judgments § 27 (1982)). This general rule is
“subject to certain well-known exceptions.” Id. (citing
Restatement (Second) of Judgments § 28 (1982) as listing
exceptions).
    Bungie devotes just two pages of its briefing to argu-
ing that the basic requirements of issue preclusion are
satisfied in this case. Appellee’s Br. 62–63. In similarly
cursory fashion, Worlds’s Reply Brief compiles a handful
of conclusory assertions in an attempt to avoid issue
preclusion. Reply Br. 30–32. And because of the timing
of the six IPRs, the Board did not consider issue preclu-
sion.
    In this case, such a limited record is insufficient for
this court to decide, for the first time on appeal, whether
issue preclusion should apply to this unusual set of facts.
The record before us is scant on details regarding the
issues raised in the three unappealed IPRs. Based on the
limited record before us, we cannot say that the “issue” is
the same between the now-final IPRs and the IPRs cur-



IPRs on November 28, 2016 (for two proceedings) and
November 30, 2016.
WORLDS INC.   v. BUNGIE, INC.                             19



rently on appeal. Bungie, of course, views the “issue” as
the ultimate determination of whether Activision is a real
party in interest. See Appellant’s Br. 63. But in our view,
the determination of whether a party is a real party in
interest may differ from one IPR to the next, even among
a set of seemingly related IPRs. Without a more compre-
hensive understanding of the issues raised in each case,
we decline to apply collateral estoppel. Instead, given
that we are already remanding this case with regard to
the merits of the real-party-in-interest analysis, we find it
appropriate to have the Board analyze in the first in-
stance whether issue preclusion should apply under these
particular circumstances. In doing so, the Board should
develop a more complete record that explains the differ-
ences, if any, between the issues raised in present IPRs
and the unappealed IPRs. The Board should also consider
any relevant exceptions to issue preclusion raised by the
parties and explain why such exceptions do or do not
apply to these facts. See Restatement (Second) of Judg-
ments § 28 (1982); see also In re Cygnus Telecomms.
Tech., LLC, Patent Litig., 536 F.3d 1343, 1349–50 (Fed.
Cir. 2008) (regarding issue preclusion where a party did
not appeal all cases consolidated in a multi-district litiga-
tion proceeding).
                                B
    Because of our conclusions with respect to the real-
party-in-interest issue, we need not address the merits of
the parties’ invalidity arguments at this time. We there-
fore vacate the Board’s merits decisions in their entirety,
without speaking to the merits of the Board’s analysis.
On remand, if the Board determines that the IPRs are not
time-barred, the Board may use its prior merits analysis
in new final written decisions, and a future panel of the
court will have occasion to review the merits of the
Board’s analysis at that time, should the parties choose to
appeal.
20                                 WORLDS INC.   v. BUNGIE, INC.



                             III
    For the foregoing reasons, the Board’s final written
decisions in these three consolidated appeals are vacated.
On remand, the Board should first address whether
Worlds is estopped from arguing the real-party-in-interest
issue. The Board should thoroughly consider the posture
of the related proceedings, as well as any relevant excep-
tions to collateral estoppel. If the Board determines that
collateral estoppel does not apply, the Board should then
reevaluate the merits of the real-party-in-interest issue.
And, in light of this court’s recent guidance on the sub-
stantive real-party-in-interest inquiry, the Board, in its
discretion, should consider whether to allow for additional
discovery on this issue. 14
              VACATED AND REMANDED
                           COSTS
     The parties shall bear their own costs.




     14See Applications in Internet Time, 897 F.3d 1336;
Wi-Fi One, 887 F.3d 1329; cf. WesternGeco LLC v. ION
Geophysical Corp., 889 F.3d 1308 (Fed. Cir. 2018).
