MArcomage

This card in combination with Priest is just too good for an uncommon/common combo. In my opinion, it shouldn't be durable or should be more expensive so that you can't just keep playing it removing a card, gaining 3 stock, rinse, repeat.

I do like the idea of replacing cards in enemy hand with ashes and making Priest a better card. Currently, Priest is really only effective against undead and too specific to be worthwhile - even in a holy deck.

Since it's only affecting the card in the matching position, the opponent could ensure that slot doesn't contain an Undead and then either deal with any single Purified ashes or play Mummy to banish this card entirely. At a cost of 10 gems, I don't think chaining it for stock gains is going to be an especially likely scenario.