Nefarious Lich

Two of the three clauses can end the game outright, and the design lives in the gap between them. Damage stops touching your life total and starts exiling cards from your graveyard instead: run that pile dry under a swing you cannot pay for, and you lose on the spot. The enchantment itself is a load-bearing wall, so any answer that catches it (a disenchant, a wrath, even your own bounce spell) does not merely strip a permanent, it kills you outright. The middle clause is the gentler one: lifegain quietly stops being lifegain and becomes raw card flow, every incidental Soul Warden point and lifelink hit converting into a draw you never paid for, with no death penalty if you simply never gain. What lifts this above curiosity is how the three clauses pull against each other. The graveyard wall demands you keep refueling a resource the rest of the deck wants to spend; the lifegain redirect rewards a build around incremental gain you would otherwise ignore; the leaves-the-battlefield clause forbids you from ever treating the enchantment as expendable. This is black's purest "your other resources are now your survival" inversion, an early-era statement that the game's two oldest counters (life and cards in the yard) are interchangeable if you are willing to bolt a loss condition to the conversion. The reward is a near-unkillable life total sitting one untimely removal spell away from a concession.