Andariel, Maiden of Anguish

Infect
-1/-1 counters can not be removed from opponent's creatures.
{4}{t}: Put a -1/-1 counter on all target opponent's creatures. If a creature already has a -1/-1 on it.
"She's a master manipulator who sets up scenarios in which the victim's mental state are twisted inside out. She loves seeing people torn apart by their own inner agony and emotional pain." - Book of Cain