Harbinger of Poisons

If a -1/-1 counter would be placed on a creature
an opponent controls, that many counters plus
one are placed on it instead.
{1}{b}{t}, Pay 2 life: Put a -1/-1 counter on target
creature.
"Our adversaries don't just include horrors and the
undead. There are some of us who still spread death
in reverence of the God-Pharaoh."
--Rytses, Deathwatch guard