Greenskull

Whenever Greenskull blocks or becomes blocked, the owner of the creature that got blocked by it or blocked it mills 3 cards.

Persist 8. (When this creature dies, if it had less than 8 -1/-1 counters on it, put a -1/-1 counter on it and return it to the battlefield under your control. The -1/-1 counters remain on the card even when it is in the graveyard.)