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
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
Heroes Reunion probably seems like an odd card to be slotted higher than Call of the Conclave, but hear me out: Call of the Conclave is Watchwolf plus
Does Casting a Card Always Use the Stack
If it later becomes a creature and damage is dealt to it, that damage won't remove any loyalty counters
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