While, as a Water player, I would love this card, this would sadly make Poison decks go bye-bye. The downside of the spell Poison is that there is only one use per card, so poison can re-stack after the Purify usage and the battle goes on. You have to time when to use your Purify - do I use it early and prevent a bit of damage early on, or do I use it later and take out a bunch of poison? With this card, this decision is gone completely. You could use it every turn, and the poison stack goes back to 0. Every turn.