i like the mechanic and the balancing mechanism, only a couple minor issues-
generally for the unupped its uncommon for the atk to exceed the cost of the card, 1:1 or worse is typically accepted
the card names seem a bit more
than
? *edit and after thinking about it, the ability seems to be more
than
, an easy fix would be to swap the two.
the art source is down currently, but at a glance im surprised it is copyright free, either from the artist or with the character portrayed being from diablo 2