Continuing to mutate on top of one or several Greathorns can really help a player get ahead on mana while also triggering other mutate abilities that have been combined with it during the game
If thats not fitting for the problem youre facing, you can also choose to have all creature tokens get -2/-2 until the end of the turn, which is going to be great against Wolf tokens, Zombie tokens, probably Human tokens and basically every other creature token too
If you spend five mana later, you can cast spells from your graveyard this turn like a Yawgmoth's Will
If they are holding removal or countermagic you can take that away, see what other options they have and then do your own thing with perfect information and safety
Sets 1-4 (The First Chapter, Rise of the Floodborn, Into the Inklands, and Ursula's Return) already left Standard in the game's first rotation, back in September 2025
For another, the decks would stay a lot more fun to play as new sets come out with room to incorporate other cards