Urazushi, Disgraced Ronin

This spell costs {1} less to cast for each Demon creature you control.
Whenever a creature you control deals combat
damage to an opponent, put a +1/+1 counter on Urazushi, Disgraced Ronin.
Whenever Urazushi, Disgraced Ronin deals
combat damage to an opponent, if that player
didn't lose the game, sacrifice Urazushi and
create X 1/1 black and red Demon Samurai
creature tokens, where X is half Urazushi's last
known power, rounded down.