Could the prologue be indicating a previous incarnation of the Mages Guild or do you think this was a mistake by the developers?
During the early part of the quest a letter to Verandis from Rada al Saran is found in a secret chamber in the Ravenwatch Castle. The letter speaks of the Mages Guild, but the quest clearly places the letter and Verandis' visit to Grayhome before the Gray Host was unleashed on Tamriel. Further proof that this is during the period of the first era prior to 1E 1029 is the mention of a possible ally in Empress Hestra. The very person responsible for deposing King Styriche of Varkarth.
Its established that the Mages Guild was formed by Galerion in the early years of the 2nd Era though it seems no exact date for this is ever given. Its not officially recognized until 2E 231 by the Guilds Act.
Even if the Guild was formed on the first day of the new Era it would still put its inception 1891 years after the events of the 1029.
Penniless Sellsword Company
Captain Paramount Jorrhaq Vhent
Korith Eaglecry - Laerinel Rhaev - Enrerion - Caius Berilius - Seylina Ithvala - Signa Squallrider - H'Vak the Grimjawl
Yynril Rothvani - Tenarei Rhaev - Bathes-In-Coin - Dazsh Ro Khar - Aredyhel - Reads-To-Frogs - Azjani Ma'Les
Kheshna gra-Gharbuk - Gallisten Bondurant - Aban Shahid Bakr - Etain Maquier - Atsu Kalame - Faulpia Severinus