Crixarg, Demon of Defiance

Flying
All Knight creatures you control gain +1/+1
and have Deathtouch.
All Demon creatures you control gain +1/+1
and have First Strike.
Whenever a Demon or Knight creature leaves the battlefield, put a +1/+1 on Crixarg, Demon of
Defiance then deal X damage to any target,
where X is Crixarg, Demon of Defiance's power.
The embodiment of free will...