Demon Lord Rimuru Tempest

{2}: Regenerate Demon Lord Rimuru Tempest.
Asimilate — {1}{w}{u}{b}{r}{g}: Exile target
creature. You may mutate that creature onto
Demon Lord Rimuru Tempest. That creatures
mutate cost is equal to its mana value. (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 under it.).