Ethereal Champion

The promise is an untouchable defender: an Avatar whose controller pays life to shrug off damage, point by point, indefinitely. The math is where the fantasy collapses. Each activation prevents one damage for one life, so the granularity that sounds flexible is actually the trap. Against a single large attacker you spend life equal to the threat just to keep a 3/4 that never grew, and against a swarm you bleed yourself dry holding a body that does not advance the board. The triple-white commitment pins it to mono-white, and even there it preserves a creature without ever threatening to win the game.

The deeper issue is structural, and it explains why pay-life prevention never matured into a defensive keyword. Prevention scales linearly while threats scale faster, so a card that reads as unkillable just converts your life total into a slow leak. Wizards eventually stopped treating life as a renewable wall to spend down and moved its durability mechanics toward regeneration, indestructible, and hexproof, all of which protect a creature without charging you per point of damage absorbed. Ethereal Champion is the older philosophy in pure form: a defensive engine that taxes the defender. The high-fantasy framing sells a ghostly guardian beyond harm; the rules text delivers a self-taxing speed bump that gets worse the more work you ask of it.