ISG (Infectious Space Growth)

Defender, lifelink
When ISG enters the battlefield and at the
beginning of my upkeep target creature gets a parasite counter.
At the beginning of combat ISG deals 1 damage
to each creature with a parasite counter. Then if
at least 5 life is gained this way sack this creature
and search for Stinger, Parasite from Space.
It enters the battlefield with haste.