Starved Rusalka

The cleanest sacrifice outlet green has ever been handed, and that is exactly the catch. Green does not usually get to convert dead creatures into resources; that is black's province, or red's, or the colorless business of an artifact engine. Here the conversion sits bare with no upside worth the activation: a green mana plus a creature for one life, repeatable but pointed at nothing in particular. What it offers a builder is the outlet itself, divorced from any payoff. The body that dies, the trigger that wants a death, the persist creature you want to sacrifice in response to its return: this is an instant-speed switch you can throw whenever the green mana is open, and the lifegain is incidental cover for the real function. The card is plumbing rather than something you cast for its own value, useful only when something elsewhere on the board pays you for the death rather than the life. The 1/1 Spirit shell is the cheapest legal frame to staple the ability onto, and the willingness to feed your own board to it one creature at a time is the whole design tension: a sacrifice engine in a color that almost never receives one, deliberately undertuned so the engine is the gift and the rate (a mana per activation, on top of the creature) is the tax.