One of the spirits that gave themselves completely; I know that much. But from where did they come? When Anu and Padomay fought, their blood made the et-Ada. So where those spirits part of the et-Ada?
Haha, so Meridia wanted to leave into the Aetherius with Magnus and the et-Ada, but he kicked her out because she was flirting with those other et-Ada? Really? Does it literally say that somewhere?
You got yourself too mixed up.
Earthbones were the et'ada that completely gave themselves to creation of Mundus. Where they came from is the same as all the other original spirits. It kind of goes like this:
Godhead---[splits in two]--->Anu and Padomay-----[combined]----->Grey maybe filled with the et'ada, the original spirits. From there, some decide to go along with Shor's plan to create Mundus, so some give themselves completely over to creation (Earthbones), some give pieces (aedra). There are those who left before Mundus was created, and wish to never get involved at all, because they abhor the idea of Mundus. Those are the et'ada that fled, causing tears in oblivion to form, which is what the stars and sun is, the holes from when those et'ada that left. They are called the Magna Ge, and the most well known is Magnus. Then there's the daedra, who I will give knowledge from the Monomyth
"Now when the Daedra Lords heard Shezarr, they mocked him, and the other Aedra. 'Cut parts of ourselves off? And lose them? Forever? That's stupid! You'll be sorry! We are far smarter than you, for we will create a new world out of ourselves, but we will not cut it off, or let it mock us, but we will make this world within ourselves, forever ours, and under our complete control.'
"So the Daedra Lords created the Daedric Realms, and all the ranks of Lesser Daedra, great and small. And, for the most part, the Daedra Lords were well pleased with this arrangement, for they always had worshippers and servants and playthings close to hand. But, at the same time, they sometimes looked with envy upon the Mortal Realms, for though mortals were foul and feeble and contemptible, their passions and ambitions were also far more surprising and entertaining than the antics of the Lesser Daedra. Thus do the Daedra Lords court and seduce certain amusing specimens of the Mortal Races, especially the passionate and powerful. It gives the Daedra Lords special pleasure to steal away from Shezarr and the Aedra the greatest and most ambitious mortals. 'Not only are you fools to mutilate yourselves,' gloat the Daedra Lords, 'But you cannot even keep the best pieces, which prefer the glory and power of the Daedra Lords to the feeble vulgarity of the mush-minded Aedra.'"
So, all in all, everything pre-Mundus were et'ada
From MK:
Meridia's holdings in Oblivion are collectively known as "The Colored Rooms". Another Prince whose origins may not entirely be outside of the aetherial, Meridia has at several times been linked to Magnus the Sun. The most famous account of this association is the Tract of Merid-nunda, which overtly casts Meridia in the role of a wayward solar daughter, cast from the heavens for consorting with illicit spectra.
What this illicit specrta could be is probably a mortal, and because of this, Umaril may have been since he was half divine and half mortal, and was known to have a link with Meridia. Or it could have been Umaril directly, but that's all speculation