Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Archfiend's Vessel enters the battlefield, if it entered from your graveyard or you cast it from your graveyard, exile it. If you do, create a 5/5 black Demon creature token with flying.
If Archfiend's Vessel leaves the battlefield while its triggered ability is on the stack, you can't exile it from the zone it's put into, so you won't create a Demon.