Rat Torturer

Whenever Rat Torturer would deal damage to a creature instead put that many -1/-1 counters on it. Creatures with -1/-1 counters on them cannot block Rat Torturer. Rat Torturer gets +1/+1 for each creature with a -1/-1 counter. Rat Torturer cannot block.
{t}: Rat Torturer fights target creature.
{b}: Put a -1/-1 counters on target creature.
{4}{b}: Rat Torturer deals damage to target creature equal to its power.