Oathsworn Vampire

Recursion gated behind a verb, not a resource. Most graveyard-castable creatures pay an explicit cost or carry a one-shot exile clause; this one grants nothing more than permission to cast it again, keyed to whether you have gained life at any point this turn. It is not a triggered ability that resurrects the body: the card sits in the yard and stays legal to cast for as long as the lifegain condition holds, which is what fits it into a lifegain shell rather than a reanimator one. A Soul Warden trigger, a point off a lifeland like Radiant Fountain, any sliver of incidental gain makes the recasting live, and then it returns tapped, over and over, for the price of its mana each time. The reward is a body that refuses to stay dead so long as the deck is doing what it already wants to do; the tax for that durability is the tapped clause, which strips the turn of any tempo the recursion might otherwise buy. It never blocks the turn it returns, never swings the turn it returns, and asks you to spend the mana before you see a scrap of value. That makes it an engine piece rather than a beater: a recurring chump, a sacrifice target that pays for itself across a long game. The tapped entry keeps the loop from being free; the lifegain permission is the leash tying it to one specific kind of board.