Flayer of the Hatebound withers all

Whenever a creature enters, that creature's controller may have it deal damage equal to its power to any target of their choice.

Players can't gain life. Damage can't be prevented. All damage is dealt as though its source had wither. (A source with wither deals damage to creatures in the form of -1/-1 counters.)

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.) Whenever this creature or another creature enters from your graveyard, that creature deals damage equal to its power to any target.