Polukranos's Hatchling

Whenever a creature an opponent controls dies,
if it was dealt damage by a creature you control
this turn, put +1/+1 counter on Polukranos's Hatchling.
As long as Polukranos's Hatchling has five or
more +1/+1 counters on it, it has trample and
reach.
Fed on the scraps of fallen heroes, a new generation of nightmares grows to threaten the polis.