Who, exactly, the Three are depends on who you ask and when, but it's generally understood that they constitute:
Aio: A goddess of light, heat, war, music, poetry, fertility, and divine kingship. She drives the sun across the sky.
Onun: A godden of storms, currents and gyres, medicine, agriculture, calendrics, divination, and craftsmanship. They drive the moon across the sky. (It is customary to refer to them with your own pronouns.)
Gaurin: A god of night, coolness, fertility, death, blood sacrifices, commerce, and the hunt. He is personified by the night sky, the "backbone of night" in particular.
The deities known as the Many are usually understood to be "everyone else": hypostases or children of the Three, and other beings. The gods in this category are too many in number to count, but a few are relevant to the story:
Aluomoc: A shape-changing god with unknown influence and association. He may rule over thresholds and liminal places due to the keys he carries, and is likely connected to the underworld and the dead because he has been seen with the head of a tube worm. His purple skin also associates him with the night.
Aiorin: A possible child of Aio and Gaurin, a goddess of bloodlust and victory in battle.
Wights: The category of small gods with very localized rule: individual buildings, towns, natural landmarks or formations in the landscape. Sometimes they're extremely powerful, sometimes not. It's generally understood that they are caretakers of whatever area they personify, whether hostile or helpful to mortals.