Moon is a winged shape-shifter who doesn't know what he is. Turns out he's one of the monsters called the Fell. (No knowledge of the books necessary)

In which Moon runs afoul of a second flight of Fell, well ahead of schedule. Written for lastwingedthing on archiveofourown, as part of Alternate Universe Exchange 2019. [Characters: Moon, Consolation, First, Kethel, Consolation's Father.]

When six consorts from Storm Fall, an outcast court spurned by the Reaches centuries ago, arrive at Ocean Winter with news of an approaching threat, Ocean Winter enters a tenuous alliance. As the court works with Howl, consort of Storm Fall, to uncover the threat's true nature, it learns more about Storm Fall and begins to suspect that Howl may have a dark secret of his own.

Progenitors are not birthed evil. Nothing is. It's what happens after that gradually makes them so. (Subject to additions if anyone likes it.)

I haven't read The Siren Depths yet so this is based on The Serpent Sea. Basically a few warriors become consorts and a new queen arrives.

Before Moon arrived at Indigo Cloud Court, the consort bower had been empty for some years and the court as a whole slowly dying. Something had to change. The three consorts of Indigo Cloud (Stone, Moon, and Ember) had had very different expectations, but the reality surprised each of them.