Battle at the Helvault
The chapter structure retells a scene: two rounds of banishing the board's threats behind a seal, then the seal breaking to release something worse. Chapters I and II each exile up to one non-Saga, nonland permanent per player, symmetrically, and here is the wrinkle: they exile until the Saga leaves the battlefield rather than until the chapter resolves. Because a Saga sacrifices itself after chapter III, that release is scheduled from the moment the enchantment lands. Everything imprisoned in I and II comes back the turn the Angel arrives, so you are handing opponents their permanents back at exactly the moment you least want them to have blockers. The Avacyn token blunts that return by being nearly unkillable in combat: an 8/8 flier with vigilance and indestructible does not care that three creatures just returned to defend. The card sets temporary control against a permanent finisher, and it forces the pilot to treat the three-turn clock as a countdown to a board reset rather than a slow value engine. Sagas that exile "until this leaves" are a small family, and most of them ask you to keep the enchantment alive; this one guarantees its own departure, which turns the exile into a delay tactic with an expiration date you cannot extend. The payoff has to be worth losing the prison, and an indestructible flying 8/8 is the argument that it is.
