Urza's Destiny

Creature — Rat

When this creature dies, target creature gets -2/-2 until end of turn.

Disease Carriers

Enchantment — Aura

Enchant creature
At the beginning of your upkeep, you may put an infection counter on this Aura.
At the beginning of the upkeep of enchanted creature's controller, this Aura deals X damage to that player, where X is the number of infection counters on this Aura.

Festering Wound

Creature — Phyrexian Zombie Dog

When this creature dies, all creatures get -1/-1 until end of turn.
{2}, Sacrifice this creature: Draw a card.