I don't think it's that far-fetched for Gaius to return. He 'died' off camera in 2.0. Ascians can possess people or whatever the proper term is. We first meet Elidibus in 2.1, right after Gaius disappeared. The Garlean emperor was shocked by the face of Elidibus in 4.0, suggesting it's a face he recognises. So... Eli possessed Gaius and teleported out of the praetorum?