Seikikaku, the Swarm Caller

Deathtouch
Whenever Seikikaku deals combat damage to a
player, you may pay {x}{w}{b}{g}. If you do, create
an X/X green Insect Swarm creature token with
"When this creature dies, put each card exiled
with it into its owners graveyard" and exile target
nonland permanent that player controls with
mana value X until that creature leaves the
battlefield.