The signpost uncommon in that set was Foggy Swamp Spirit Keeper, a typical draw-2 payoff that spits out 1/1 spirits which can only engage in combat with other spirits
Starter 2 Player Starter Set player guide
Its a Sorcery First and foremost, Slime Against Humanity is a sorcery, which is a relatively rare trait for cards with no inclusion limit
Not only do these give you more things to do in every game, but they could help mitigate discard from spells like Cathartic Reunion, or give you extra value from getting milled (intentionally or otherwise)
Tonys store is huge and it buys a lot of Magic cards from its community, so its important that he and his staff understand how to spot a fake
In Modern, Preordain was primarily used to fuel combo decks for the brief window where it was legal