Whenever Genghis Frog or another Mutant you control enters, create a Mutagen token. (It's an artifact with ", , Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")
"Free our brothers! The human reign of terror around here ends tonight!"
, 
, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")
