While resting in the dungeon, the group fails to notice nightmares hide alongside them during the journey. They discover it quickly— after Mithrun is induced to sleep, and see he's immediately uncomfortable.

In his dream, he doesn't know he's affected by a nightmare. He just thinks he's reliving his horrid incident of being under the Winged Lion's influence and failing to keep the dungeon afloat. He's stuck in that earlier mentality, having no memory of the fact it's already been years since.