Omblakar, The Desolator

{b}, Reveal Omblakar, The Desolator from your
hand: Put a doom counter on target creature
with no counters on it. Activate this ability any
number of times each turn.
Omblakar, The Desolator costs {1} less to cast
for each doom counter among permanents.
When Omblakar, The Desolator enters the
battlefield, destroy each creature you don't
control with a doom counter on it.