This is a cool idea, very in keeping with Aether's style. It seems balanced. It may even too expensive. Compare to Mirror Shield, which reflects spell damage but doesn't affect poison, voodoo or catapault. I consider the two abilities to be about on par, and Mirror Shield costs 2 less upgraded. Unupgraded, it should ptobably cost 1 more than Skull Buckler, which is it's nearest counterpart. Neither of those two comparison cards are edgy, so I think a drop in cost for this is more than fair.
Other than that, I love this idea. It'll be nice for Aether to have a shield that isn't on a timer.