Since when does Caliborn only exist post retcon? I thought he was present before that
Caliborn is from the future of the Alpha kids’ timeline, his existence is dependent on them creating a new universe explained by Aranea here. In the Pre-retcon Game Over timeline everyone dies and they never create a new universe so Caliborn never hatches. And yes he was present early in the story before the retcon happened but he was always in the far off future.