Requiem Angel

The exclusion clause is the whole machine. Most token-on-death payoffs would spiral out of control feeding themselves, but this one carves out Spirits from its own trigger: the 1/1 fliers it makes never beget more, so the engine stays bounded to the bodies you actually sacrifice or trade away. That single word, non-Spirit, is what keeps the card from being a self-sustaining loop and instead makes it a converter, turning every fair-creature death into a flying threat that holds the ground above. The design rewards a board built from disposable non-Spirit creatures: each one becomes a replacement that flies, so combat math and chump-blocking both quietly shift in your favor. Among white death-replacement effects, the kind that punish an opponent for the very removal and combat trades they need to make, most hand you a flat token; this one specifies flying, layering an evasion engine on top of the attrition. The 5/5 flying body is almost incidental to the text, a reasonable clock that happens to dodge ground stalls while the Spirit factory hums underneath it. The structural cleverness is that the exclusion is doing two jobs at once: it caps the recursion, and it implicitly directs you toward a deck of expendable groundlings whose deaths read as upside rather than loss.