Board Thread:Lore Discussion/@comment-27673129-20170414055455/@comment-1255618-20190316043550

Tickytickytango wrote:

This is the only time (that I know of) that an Aedra ever became a Daedra in this way.

TL;DR: Meridia used to be an Aedra, she became a Magna Ge after following Magnus away from Mundus. She became a Daedric Prince after consorting with the Daedra. You're forgetting how Malacath is considered a Daedroth even though he used to be the Aedroth Trinimac (like Sothas pointed out). Maybe the reason he's considered one of the Daedra is that Malacath isn't exactly the same as Trinimac but was "born from" him (or rather, his reanimated dung) and therefore now has more traditional Daedric properties.