Originally Posted by
Fox
SnT quite importantly keeps you on color (UB core) allowing you to reach a wasteland-immune 2mana base, pitches to force, and all but requires opponents to aim a counterspell at it (which basically qualifies it as a counterspell vs a non-proactive blue deck). Abrupt Decay, while a strong card upon resolution, has glaring weaknesses before you even cast it both on the mana-base side of things and inability to advance your ability to win. Decay is the kind of card you want out of your hand the moment you draw it; if it's not helping you win then and there, its being drawn is the main reason you're losing. Decay makes a very strong case for maximizing post-board hand correction effects and flip-jace in the deck, turning the preferred casting zone of this sideboard card to 'from the graveyard,' a post-board strategy that has foreseeable issues.