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I have always played this curse as an "At any time" ability vs having to be used upon activation. I believe this card was meant to be used at any time in battle , as Covenant of Noah is (errated). I want to verify with the elders if Unsuccessful is to be treated like errated Covenant of Noah.
Sorry, to ask a noob question but is there a list of erreta cards? Or did I overlook it in the REG?