The actual cards in Un-sets have a bunch of silly effects and abilities.
Certain cards that won’t be for “regular” black-bordered play will instead have an acorn security stamp to indicate their Unfinity origins. The silver border on Un-set cards is replaced with a black border in Unfinity to encourage their use with other black-bordered cards. The cards aren’t covered by the comprehensive rules and are “not for tournament play,” notably different from being not “tournament-legal.” While it’s true that silver-bordered cards aren’t legal in any Standard, Vintage, or Modern decks, Wizards still intended them to be used in casual black-bordered formats rather than exclusively with each other. The Un-sets are MTG sets of (formerly) silver-bordered cards with jokey and fun effects that parody Magic, the players, and the game’s history. Double Header | Illustration by Richard Sardinha