Caustic Tar

Six mana to turn a land into a repeatable three-point clock is the kind of math that only makes sense once you stop thinking about racing and start thinking about inevitability. This is a win condition built for the control deck that has already locked the game up: the board is stalled, the opponent is out of threats, and you would rather not draw into a creature that might trade or die. Attaching the clock to a land rather than a creature is the whole gambit. Lands sit outside the removal most decks pack, so once the Aura resolves, the only outs are enchantment hate or a way to destroy the land itself, neither of which a lot of decks run by default. The cost is the slow speed: three life lost per turn means seven activations to close from twenty, which is glacial, but a control deck that has stabilized is in no hurry. The ability strikes a player directly rather than dealing damage, so it cannot be aimed at a planeswalker or anything else; it simply grinds a life total down regardless of what stands in the way. Land-enchantments that grant a damage-by-proxy ability are a small and mostly forgotten design pocket, and this one lingers in memory as the one that did the idea no harm: a do-nothing-now, win-eventually engine that asks only that you live long enough to keep tapping it.