Did anyone else recognize, that if you use that card, and the opponent can play it even once, then both hands (of you and your opponent) will get filled with this card whenever a creature dies. So this card counters itself if you play against another death deck or a rainbow deck.
I am not sure how to balance a card like that. but it should definitely do something nasty if you discard it like infect a random creature card on your side of the field (or damage yourself, like suggested already.)