Serum Powder

Before the London mulligan rewrote how openers work, this was the only card in the game that let you fix a bad hand without losing a card. The trick is buried in the second ability: exiling your hand and redrawing the same number is a free hand-swap that does not cost you a card the way a traditional Paris mulligan does, and crucially it stacks on top of your normal mulligans. That made it the canonical consistency engine for hands that need a specific opener and cannot afford to ship cards to do it: combo decks chasing a turn-one kill, decks built around an artifact lock, anything that would rather see eleven or fourteen cards than play a real game from six. The mana ability is almost a formality, a colorless rock stapled on so the card is not a literal blank if you keep it. The real cost is the exile clause: the swapped hand is gone from the game, not shuffled back, so every redraw thins your library of the cards you bin and removes them as future draws. That permanence is what kept it honest before mulligan rules caught up; you were trading raw card access against a deck you were actively hollowing out. The London mulligan eventually made this kind of digging available to everyone for free, which reframed Serum Powder from a singular tool into a relic of an older consistency math.