The Elder Scrolls V: An Empire in Ruin
How many times do the Elder Scrolls come up in game? As far as I know, only Oblivion does it. Once.
As in make an appearance? Only Oblivion. And Arena might too, but who takes notice of Arena? I think it wouldn't be unlikely that when the decoded package in Morrowind talks about the emperor consulting with "his most expert informants and confidants", he might be talking about Moth Priests and Scrolls.
I think there's also implication that each game is itself an Elder Scroll about the actions of a hero, hence the the title. Except Morrowind, which was, in fact, "a linguist- launch cell from the last Shipstar, ex-Engine'd, made by the hands of beautiful people." Yeah.