Zekito, The Anomaly Gene

Mutate {4}{u}{g}
Trample, Provoke
Whenever this creature deals excess damage to a
non-Human, non-commander creature, exile that
creature. It gains "Mutate {0}" and "This spell
must be cast for its mutate cost. While choosing
targets as part of casting this spell, you must
choose a commander you own." You may cast
that spell.