Kenrith, Witch of the Mirror

Whenever another nontoken creature enters
the battlefield under your control, you may
pay {g/w}{w/b}. If you do, create a token that's
a copy of that creature.
Whenever a nontoken creature enters the
battlefield under an opponent's control,
you may pay {b/g}{g/u}. If you do, create a
token that's a copy of that creature.