Archon of Absolution

The pillow effect here is doing two different jobs at once, and both of them are tuned for a defensive white body. The tax on attackers is the same structural idea that Ghostly Prison and Propaganda built their pillow-fort reputation on: attacking becomes a resource question, not a combat question, and a swarm that would happily trade into a small blocker suddenly has to price out every creature in the pack before it commits. Stapling that to a 3/2 flier means the deterrent walks in the air while the ground stalemate holds. Protection from white is the wrinkle that makes it durable in its own color's mirror: it slips past white blockers, shrugs off white removal, and dodges white auras and equipment aimed at it, which is a pointed choice for a card whose main threat is other white weenie decks trying to punch through. None of the three abilities is expensive on its own; the design sits at the intersection, where a flying clock, a tax that slows the race, and a resistance to the color most likely to be attacking you all reinforce the same posture. It is a defensive keystone that also happens to end games if the board sits long enough, which is a harder combination to build than the modest rate suggests.