Does that make the deeper a dragon? A sea serpent? Something else completely?

"So, basically we have something big, angry, and powerful about to bust free from under those bones," Billie reiterates this -- slowly -- for the sake of the knights and others on the boat with her. "Is that what broke the bones? Is there a way to, you know, maybe convince this deeper to go back to sleep under them or just help it on its way rather than the whole 'destroy everything' deal?"