Furious Reaper

Menace, restless (When this creature dies, if it is not
a Spirit, return it to the battlefield under its owner's control. It becomes a Spirit in addition to its other types.)
When Furious Reaper enters the battlefield, each player sacrifices a creature. Then if Furious Reaper is a Spirit, it deals X damage to each player, where X is the number of creatures sacrificed this turn.