Daemonium, the Watcher

Flash, Flying, Deathtouch, Menace
Daemonium costs {1} less to cast for each spell
your opponents have cast this turn.
When Daemonium enters the battlefield destroy
target creature or planeswalker.
Whenever you cast a spell exile Daemonium
unless an opponent pays 3 life. If you do, return Daemonium to the battlefield at the beginning of
the next end step.