I know this topic includes Elder Scrolls Online information, but it also encompasses info from the main Elder Scrolls series (there was also no lore section in the ESO forums that I could find). In Oblivion and Skyrim, the book 'Mannimarco, King of Worms' by Horicles states that Mannimarco was the "world's first of the undying liches."
However, in Elder Scrolls Online, which takes place while Mannimarco is still a mortal and had not yet become a lich, there are already liches running around in the game. There is even an in-game book in ESO called 'Ascendancy: Pathway to Lichdom' written by Gullveig the Ascendant that details how to become a lich.
So is Mannimarco not the first lich in Elder Scrolls lore anymore? (Maybe Gullveig is actually the first?) Has this discrepancy ever been explained in Elder Scrolls canon?, i.e. Horicles made an error in his book, or some other retcon? Just curious, thanks.