The dream-space where Carl watched Shi Maria devour Hapanzi and learned the rules of her containment.
Carl repeatedly cross-references the dream against the ballroom replay. In the dream, he and the others watched Shi Maria devour the human version of her husband while screaming that she loved him and would never hurt him — which is why he alone recognizes the unhinged jaw in the replay and the moment Hapanzi's leg vanishes from her mouth.
At that exact moment in the dream, Shi Maria disappeared and Hapanzi reappeared as a spider, telling Carl she was gone, trapped in his own body, and that he now controlled The Eye of the Bedlam Bride and her containment — summonable once, with the choice hers. She had returned before Carl awakened, and they had left her in the room with Annie. Carl's conclusion: Shi Maria is now yet another bomb in his inventory, an especially dangerous one — and she did not look nearly as trapped as Hapanzi claimed.
The dream-encounter that established Shi Maria's imprisonment and the eye's single-use rule.