Hidetsugu's Second Rite

The exact-10-life clause is the whole joke and the whole problem: a four-mana instant that does nothing against any life total except one, and that one total almost never occurs on its own. What you are buying is a finisher gated behind a setup step, and the setup is where the card becomes a puzzle box rather than a burn spell. It can only target a player, not a creature or planeswalker, so it never functions as removal; it is purely a way to end someone once they have been walked to the precise number. That march to 10 is the deck's real job: pairing this with damage you can meter to the exact point, a Browbeat that deals 5, a Sulfuric Vortex tick you can count, repeated symmetrical pings you can math out. Get them to 11 and the spell whiffs; overshoot to 9 and it whiffs the same way. That brittleness is the design tension. Most burn rewards approximation; this rewards arithmetic, and it punishes a missed count with a dead card in hand. The payoff for threading the needle is a 10-damage swing for four mana, a rate no straightforward red spell would ever be allowed to print, which is exactly why the condition is so unforgiving. It is a combo enabler wearing the silhouette of a burn spell, the kind of conditional payoff that asks the deck around it to do all the real work and then closes the door in a single instant once the work is done.