Zac, the Ooze Weapon

When Zac, the Ooze Weapon dies, exile it create
X 1/2 Z-Ooze green tokens with Ward {1} and
"at the beginning of your upkeep, if Zac, the
Ooze Weapon is in your exile, you may sacrifice
all tokens you control and return it to the battlefield with X plus two +1/+1 counters,
where X is the amount of tokens sacrificed this
way.", X is Zac power.
{4}: Return this card to your hand from exile,
activate only if you control no Z-Ooze tokens.