Artuk, Mind Feaster

Whenever Artuk, Mind Feaster enters the battlefield, each opponent sacrifices a creature.
Whenever Artuk, Mind Feaster attacks, each opponent puts the top 8 cards of their library into their graveyard. For each non-land card put into a graveyard this way, put a +1/+1 counter on Artuk, Mind Feaster.
Whenever Artuk, Mind Feaster blocks, draw 4 cards.