Bile Urchin

The body is incidental: a 1/1 Spirit that exists only to be sacrificed. What it actually sells is the conversion of a creature into a single point of life loss at will, and that exchange is the whole design. Drain-on-sacrifice was an old idea by the time this Spirit arrived, but earlier versions tended to charge mana for the activation or do the draining themselves; here the cost is free, and the only resource spent is the creature you were already planning to lose. That makes it clean aristocrat fodder, a body that wants to die and pays you for the privilege, and it slots into any engine that recurs creatures or counts death triggers. The single point is small, which is exactly why the design holds: a creature that surrenders one life on the way out is fine, while one that drained more would warp the math around any sacrifice loop that brings it back. Note that it is life loss, not damage: nothing prevents it, no creature blocks it, and it ignores any effect that cares about combat or damage sources. It does no work in a vacuum and was never meant to. Its job is to be the cheapest possible token of value in a chain of effects, the reusable trickle that only adds up when something is feeding it back to the battlefield.