Wow. Opponent cannot play any aura's ever? Seriously harsh for an uncommon.

(Well, technically they can play them; they just can't ever keep them.)

I'm not sure making it rare actually helps. The existence of this completely invalidates Auras; and they were already quite marginal.

Mmm. Not really, because this card is itself only actually playable in a deck if Auras get strong enough :) It's like Leyline of the Void. You don't maindeck it in casual because it'll usually be a dead card; but you sideboard it, or bring out your tailored anti-tech deck, against the decks that really abuse the mechanic it hoses.

Or like Circle of Protection: Blue, I suppose. It really hammers the deck it hurts, but wouldn't normally be put in a deck in the first place... unless it is... then, you know, game over.

Changing it some. here is the original text for comparison. "Destroy target aura. At the beginning of your upkeep if there is an aura on the battlefield, return Aura Errosion to your hand."

I;m making it slower and an option to retrieve it.