Darius, Hand of Noxus

Wither, Menace,
If Darius blocks or is blocked by a creature with
a -1/-1 counter on it he gains first strike until
end of combat.
Whenever Darius kills a creature, you may pay {b}{r} if you do Darius kills target creature with
a -1/-1 counter on it.
"Exploit every weakness."
-Darius