Good idea! I like the way you've used a non-offensive move with a creature, esp. with 0 attack. FYI, i think there is a space before the ":" colon in the top line. I think this version if quite fair, having a medium/high cost for a good effect that can kill monsters AND poison. However, this will look kinda crap (no offence) when you see Maxwell's Demon, which can attack and kill higher strength creatures. Apart from the kinda screwed maxwell's demon, you're good.