Genghis Frog
Legendary Creature — Frog Mutant Rogue, {G}{U}
Oracle Text
Trample
Whenever Genghis Frog or another Mutant you control enters, create a Mutagen token. (It's an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")