Okpu, the Mercury-Form

Mutate {1}{u}{u}{c} (If you cast this spell for it's
mutate cost, put it over or under target non-Human creature you own. They mutate into the create on top
plus all abilities from under it.)
Changeling
If Okpu mutates on top of a Shapeshifter, create
a token that's a copy of that creature.
This creature's power and toughness are equal to
the number of cards in your hand.