Koth, Savior of Mirrodin

Double strike
When Koth, Savior of Mirrodin attacks, up
to 2 target creatures gain double strike.
At the beginning of your post-combat main
phase, if you attacked with 3 or more creatures
this turn, you may exile Koth, Savior of
Mirrodin then return it to the battlefield
transformed into Koth, Mirrodin's Rage under
it's owner's control.