Wartortle

Mutate {3}{u}(If you cast this spell for its mutate
cost, put it over or under target non-Human creature
you own. They mutate into the creature on top plus
all abilities from under it.)
---{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}{dash}
Whenever this creature mutates, if it mutated
onto Squirtle, put a vigilance counter on it