The Numen are the oldest known race, predating the Cleansings and the Dawnborn, Valuren, etc. They are not one specific species, but a collection of species of shared origin akin to the all elves, dwarves, and humans being under the ‘humanoid’ umbrella.
When the Luminos fell, the Numen fought a war amongst themselves. Some wished to devour its light, and in so doing became monsters. These were called the Elder Darks while the Listeners who wished to observe and worship the great creature contested them. The Incarnates seem to have been Numen who drank the light too greedily.