Flying
This creature enters with two +1/+1 counters on it.
Whenever another creature dies, put a +1/+1 counter on this creature.
Illustrated by Monztre · Khans of Tarkir · #92y
There are no rulings for Swarm of Bloodflies.
Whenever another creature dies, you may put a +1/+1 counter on this creature.
This creature enters with two -1/-1 counters on it.
, Remove a -1/-1 counter from this creature: Put a -1/-1 counter on each other creature.
Whenever another creature you control dies, put a +1/+1 counter on this creature.
Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever a creature dealt damage by this creature this turn dies, put a +1/+1 counter on this creature.
, Discard a card: Put two +1/+1 counters on this creature.
, Sacrifice another creature: Put a +1/+1 counter on this creature.
Whenever a creature you control with a +1/+1 counter on it dies, draw a card.