Diseased Vermin

Diseased Vermin

Creature - Rat | Power/Toughness: 1 / 1 (CMC 3)
Whenever Diseased Vermin deals combat damage to a player, put an infection counter on it.
At the beginning of your upkeep, Diseased Vermin deals X damage to target opponent previously dealt damage by it, where X is the number of infection counters on it.