I've beaten Ryth and the three titans in the sky cages. However, every time that I've been back to the sky cages (or the room where Ryth normally paces), those places are *empty.* Ryth's room has the big chest, and his ship is there, but he's missing. In the sky cages room, there are no blue circles to tap next to the three cages-- just the exit option.
My understanding is that it should be possible to face these four titans again. So, what's the trick? (Yes, got solar trans weapons, level 207, NG+/3...)