How would a Vorthos Player deal with Standard Player with Universes Beyond card?

Given that Final Fantasy is a part of Stander, along with other Universes Beyond set like Marvel's Spider-Man and Avatar the Last Airbender, I feel like I need to know how you a Vorthos Player, will deal with any Player that used Universes Beyond as part of Standard? Given that those Universes Beyond cards doesn't truly existed within Magic's multiverse.

Do you just pretend those Cards are represented a unseen SLX program version of that cards? Have it that those Franchise does existed within the multiverse or outside it by the Edge? Have it that the opponent Planeswalker casting some "made up" spells? Or you wouldn't really care any who?