Craglorn is out, but nobody's talking about Celestials yet. Why is nobody talking about Celestials yet? I expected better of you, Lore Forum.

What are they? Magna-Ge? Something else? What are they doing? Why are they doing it?

Well, I haven't played it, and I know that there are a lot of bugs that people are waiting to get fixed before they set about it.

However, I can say the following based on extant lore: the Celestials, I think, are related to old Yokudan deities. As noted in Varities of Faith, the Yoku Magne-Ge are, as in other pantheons, considered guides that teach mortals to transcend the Mundus:

However they seem to have at least the same constellations as mainland Tamrielic religion (perhaps evidence against Nirn being round, btw?) - although Yokudan, the Celestials are based on the familiar Guardians and the Serpent.

From the one picture I saw, I think that Serpent iconography features in the design of the Celestials. Now serpents in Yokudan myth are generally always demonized: Second Serpent Sep is a trickster and a fool, Diagna is the god of the "Twenty Seven Snake Folk Slaughter", and in PGE1 Satakal cultists are generally a dangerous nuisance to both the Alik'r and the settled coastal Redguards. Note that the Satakal worshippers are described as "revered madmen", so it could be that they represent a dangerous yet holy facet of old religion, much like Shezarr only exists in obscure cults of Cyrodiil. So while Sep is bad, Satakal is at least a force worthy of respect to them.