Parasite

Parasite is a . You can end up catching this one from events, or be implanted with a Parasite by the Writhing Mass.
Any method of permanently removing this card from your deck will cause you to lose 3 max HP. Aside from this, it's identical to an - that is to say, annoying but usually survivable. 
==Sources==
*Hypnotizing Colored Mushrooms
*Writhing Mass