The Creators and Ragnarok
The Creators, genetically, were human. A dying species, (the only name given being the Progenitors) which was far more advanced than any other species ever known, took the human genome and created a population of roughly 7 billion. This was the original purpose of Asgard, to act as a giant, hidden cloning facility and eventual home for the cloned population. The Progenitors soon died out, and the Creators were left with their technology as their only legacy.
It is also worth mentioning that Creator culture was formed around an early incarnation of Norse Mythology and legends, passed down from the Progenitors.
Soon enough, the Creators created the Pendramar, yet they rebelled, and fearing that these malevolent machines would be responsible for the Day of Ragnarok, they left 750,000 of their people, all volunteers, on Earth as an insurance policy and fled beyond the Heimdall Veil, their name for the Galactic Far Rim, into the Void. Here they were to encounter the machine responsible for the corruption of the Pendramar, Drazzana, an ancient and powerful being, intent on wiping out all organic life.
Were it not for an encounter with this old machine, the Pendramar would have never turned against the Creators.
It was soon able to turn them into an enslaved machine race, with powerful new technologies that make the Pendramar seem like toys in comparison.
Collectively, they call themselves Ragnarok, and their standard introduction is, "We are the Squires of Ragnarok, heralding the day when fire brings world's end. We are the Harbingers of your Destruction. Prepare for ascension."
The Progenitors toiled for centuries in an attempt to create their idea for a perfect race, using DNA from both themselves and humans. They were unsuccessful in creating anything they considered more perfect than humanity or themselves, and most of the scattered, "failed" remnants of their experiments remained behind as sapient life in the form of Klingons, Vulcans, Romulans, Ferengi, Bajorans, Cardassians and the countless other humanoid species that roam the galaxy.