Invocation of Doom

Whenever Invocation of Doom or a Demon
enters the battlefield under your control, you
may put a doom counter on any number of
target nondemon creatures.
Creatures with doom counters on them have
"All creatures able to block this creature do so."
Whenever a creature with a doom counter on it
dies, put a +1/+1 counter on target Demon you
control. If you do, draw a card.