Deadly Swarm

Insect Swarm comes into play with X counters.
At the beginning of your upkeep, create X 0/1 Insect creature tokens
Insects you control have "When this creature dies, create an 0/1 Insect Creature token. You lose 1 life."
If Insect Swarm is in the Command Zone, at the beginning of your upkeep create an 0/1 insect creature token