Living Artifact

The trigger condition is the whole story: this Aura cares about damage dealt to you, not to the artifact it sits on, which makes the host essentially a parking space. Attach it to any artifact on the battlefield (the enchant clause does not restrict it to your own), then bank incoming damage as vitality counters and bleed them back one life per turn at upkeep. The conversion is one-for-one and the upkeep restriction caps the drip, which is what kept a single-green damage-to-lifegain loop honest enough to print. The artifact requirement is flavor and color-pie cover rather than a strategic axis; nothing about the artifact feeds the engine, which is why the whole thing reads as a trigger looking for a host rather than a card built around one. This is early Magic inventing its vocabulary in public: stapling a novel "whenever you're dealt damage" condition onto an Aura and trusting the deckbuilder to find a damage source worth banking. Later designers tightened the lifegain-on-damage idea into permanents that needed no host, with Well of Lost Dreams converting card draw and Children of Korlis cashing out life in a single burst. Living Artifact is the fossil that came before that consolidation: a slow, conditional engine that asks you to take pain on purpose and trusts you to figure out why.