Grave Servitude
Most Auras balance their power against the risk of card disadvantage: spend a card to buff a creature, and a single removal spell answers both at once. This one negotiates on a stranger axis entirely. The drawback is keyed to when you cast the spell rather than to anything the permanent does once attached. Cast it at sorcery speed and it behaves like an ordinary enchantment: a permanent buff that swells a creature by three power, shaves a point of toughness, recolors it black, and sits on the board indefinitely. Cast it the way the design wants (mid-combat, in response to a block, at the end of an opponent's turn) and the bonus comes on loan: the Aura strips itself off during the following cleanup, leaving the creature behind but the buff gone. That choice happens the moment you announce the spell, not when it resolves: pay full freight for a lasting enchantment, or borrow a combat swing you know will evaporate before your next turn. The +3/-1 spread is what makes gaming the timing worthwhile, because the toughness hit can be lethal on a small enough body well before the Aura ever needs to fall away. The text on the creature stays constant; the cost shifts entirely with your timing, turning a plain stat-line buff into a single-use ambush whenever combat asks for it.
