Keeper of Secrets

Cast-from-anywhere is a strangely specific trigger to build a red beater around, and that specificity dictates everything else the design does. First strike and haste on a 6/4 make it a fine attacker on its own, but Symphony of Pain only pays out when you fire spells from somewhere other than your hand: flashback and its kin, cascade hits, foretell casts, adventures, spells stolen off an opponent's library, anything cast from a zone that isn't your hand. In a stock deck it does nothing beyond swing; in a deck built to launch its threats from graveyard and exile, every one of those casts becomes a bolt to the face scaled to mana value, which means the most expensive things you recur out of the bin hit hardest. That inverts the usual incentive: normally you cast big spells to do big things, and the damage rider is incidental; here the damage is the reward for having built an engine that never touches your hand in the first place. The demon is less a threat than a payoff meter, a way to convert an alternative-casting shell into reach that closes games the ground attack cannot. Outside that shell it is a large hasty body and little else, which is precisely the line the design walks: an enormous ceiling gated behind a deckbuilding demand most red decks have no reason to meet.