Ancano was an agent of the Thalmor during the Fourth Era, serving as an advisor for Arch-Mage Savos Aren of the College of Winterhold, situated in the province of Skyrim. Ancano was involved in a plot against the College, attempting to take control of the Eye of Magnus.
During the Skyrim Civil War in 4E 201, the Thalmor had a presence in Skyrim, all throughout West Skyrim. But since the College of Winterhold is a separate entity from the eponymous city of Winterhold, the Thalmor had intervened, where Ancano was appointed the advisor of the Arch-Mage, Savos Aren. Ancano's presence in the College was unwelcomed, many of the students and teachers were displeased, and he would be in constant clash with the Master Wizard, Mirabelle Ervine. At one point, a new Apprentice of the College had arrived, taking part in an expedition with Alteration teacher, Tolfdir to the excavated ruins of Saarthal. From there, the College retrieved an artifact called the Eye of Magnus, a large, mysterious orb of magical properties. This was the beginning of Ancano's plot against the College.
As time went on, both the College and Ancano started to study the Eye of Magnus, as the Apprentice sought information on the Eye, even commuting with the Augur of Dunlain, a student of the College many years ago. When the Apprentice had finally gathered enough data, Ancano had proceeded his plan, taking control of the Eye and casting out Savos Aren and Ervine from the Hall of Elements. After the two were able to break the barrier and confronted Ancano. Before they could do anything, Ancano released an explosion, killing the Arch-Mage and releasing magical anomalies in Winterhold. As the College subdued the threat in the city, the Apprentice was sent to the Labyrinthian, where they garnered the Staff of Magnus. Ancano had sent Estormo, an Agent of the Thalmor to defeat the Apprentice, but it proved in vain. With the Staff of Magnus, Ancano was killed and the College was saved. The Psijic Order had appeared before the College and eventually took it back to Artaeum for further study.
Because of Ancano's actions, hate towards the College of Winterhold had increased. Considering Winterhold's already weakened state, the explosion caused by Ancano's tampering with the Eye of Magnus had worsened Winterhold's condition. But on the positive, Ancano's tampering prompted the Psijic Order to take action, bringing it to faraway Artaeum. With the Eye of Magnus in far more capable hands, the magic world could very well learn more from it. But with the death of both Savos Aren and Mirabelle Ervine, the Apprentice was promoted to Arch-Mage, and Tolfdir was made into a Master Wizard. The Dominion had lost their connection with the College of Winterhold and was unable to garner any information on the Eye of Magnus, but with their Agent dead, the College would have likely been targeted by the Dominion.