Groaaaaag, Hungry Monster - Unknown Event

Commander Suspend 4 — (You can suspend this from your hand or the command zone. If it's your commander, command tax applies to the suspend. The rest all works like suspend.)

Whenever Groaaaaag, Hungry Monster attacks, you may sacrifice any number of other creatures. Draw that many cards, gain that much life, and put that many +1/+1 counters on Groaaaaag.