Black Knife Assassin

Trample, Death 3, Deathtouch
Sneak—(Whenever a creature without sneak
blocks this creature give this creature a
+1/+1 counter.)
Whenever Black Knife Assassin enters the battlefield all creatures you control gain death 3
and deathtouch until end of turn.
At the beginning of combat pay {x} then Black
Knife Assassin gains death 1 equal to X until end
of turn.