Board Thread:Lore Discussion/@comment-27673129-20170414055455/@comment-9212235-20170414221543

Aramithius wrote: I've never heard any suggestion.That she could be an Aedra. The Exegesis of the Merid-Nunda suggests that she was a Get, who created her own Deadric realm. Quite why this happened, we don't know. We do know, sort of. From the old version of the Exegesis, we know that Magnus banished her for "consorting with illicit spectra" which translates to Daedra. Which Daedra, is a bit more of a mystery. There is some evidence from Mankar, and a couple other sources, that we can point to that this spectra might have been Dagon.

For OP: It is important to note that Aedra and Daedra are Mer words, so anyone the Mer consider non-ancestors are Daedra. By their definition, Lorkhan is Daedra (and also by Mankar's). the Magna-Ge are a separate entity entirely. As far as how one can change, from all the evidence we have, the thing that changes is where they call home. Trinimac/Malacath is a good example here. If Malacath is actually Trinimac, then he is also Aedra, but lives in Oblivion, and is therefore Daedra. This same rule applies to Meridia. Once a Get, now a Daedra.