CURATOR COMMENT
Minor nitpick (doesn't really matter since your card technically qualifies) - the use of the word, "its" differs from "it's", as the former implies a possessive form of an object, while the latter is a compression of the clause 'it is'. Fix that in your card description/table when you can.
Not a bad concept, but just one question - does this reduce CURRENT hp, or FULL hp? (One of these will drastically increase the effectiveness of a Voodoo Doll... >.>)