Lorinth has been mostly a conceptual character for a long time. The idea of him is introduced in Book III: Traipsing Light and Shadow, and he is mentioned again in Book IV: The Distant Isles of the Dark Seas, but who and what he is remains a mystery.
The image above shows Lorinth in the distant past. He was fae, and a bringer of light. He was a member of the hidden tribes of Kriilani, far beyond the crystal mountains, in the mystical forests. I’m coming up with more of his backstory, but I can’t share much here without giving spoilers.
Lorinth will be mentioned more late in Book IV, and he will play a larger role in Book V (title not yet determined). You’ll eventually learn why he’s so important to both Eleanor and Sir Loracaz III.