Caller of the Swarm

When Caller of the Swarm enters the battlefield,
exile up to X creature cards from your graveyard,
Caller of the Swarm enters the battlefield with a
number of +1/+1 counters equal to the total
toughness among the cards exiled this way
When Caller of the Swarm Leaves dies, create a
black and green 1/1 insect creature token for each creature card you own in exile