Most fantasy writing has some kind of ancient or super powerful society or civilization where its sole purpose is to contrast how fallen or different the current one is. Lord of the Rings has the Arda, etc. I could give more examples. The Forsaken Isles have the Eldar.
The Eldar difference is that they are not a society. They were the first intelligences to form after the swirling miasma of "stuff" that would become the universes coalesced into something. Some of this was creative and would become Pha Rann and the Heavens. Others would become Chaos/Abyss or Warp/Evil. This triangle around the world is why Time (linear time the way we experience it) began to flow. It flows from our past to our future. Eventually, we die and pass through what my stories call the Gates of Oblivion, or the Anti-Life or the Shadow Realms. It's really just a place where "stuff" loses its ability to act and be acted up. Becoming inert, it eventually recycles... but lets not get crazy and call this reincarnation.
When Time first moved, the Eldar who did not ascend and become gods - by claiming a timeless dominion - fell. The Forsaken Isles has therefore three types of sentient races:
Eldar who persisted in spite of time's flow, like Alerius and Syliri
Mortals who can ascend if they come to know a timeless dominion, like Rojo... these are the mortal races like Humans, Halflings, Elves, et al
Fallen, who used to be eldar but fell and became mortal; with the proper help, these "monsters" can regain their sentience
"But, without Time, how can there be a First?" you ask. Good question. I'm not an Eldar neither are the characters. Those who are, now perceive linear time and have come to terms with it... the way you might come to terms with a terminal illness. Even for Alerius, there was a yesterday, today, and tomorrow. If you go back far enough into his yesterdays, you get to when Time moved... before that, there are events that happened with permanency. If you talked to Alerius about it today, he'd struggle to not discuss it in a linear time-driven way: this happened, then this happened.
Not all eldar have an agenda for the world. For example, Syliri was an eldar fixated with the permanency of stone. She had gathered together many others like her who danced between chaos and the elemental plane of earth. When Time flowed, all the eldar went a bit crazy. Syliri became trapped by linear time in the form of a medusa. Alerius saved her from falling. All other medusae fell. Alerius wants Syliri to ascend and become the Goddess of Medusae... but there is not a Tehran free will and sentience amongst the fallen to give that dominion any real power. So, she persists and aids Alerius with his dominion.
If the eldar stay in the world too long - and use their eldar powers - they too will fall. This is why Alerius and the dragons rarely use overwhelming magic and Alerius has specialized in human magic.