Further, Dagon assisted Tharn by attacking the Imperial Battle College in the Battlespire.

During the Imperial Simulacrum, in the years 3E 389- 3E 399, Lord Dagon conspired with Uriel Septim VII's powerhungry Battlemage Jagar Tharn to imprison the Emperor in Dagon's plane of Oblivion while Tharn assumed the Emperor's likeness and ruled in his place. Dagon cursed Chimere by twisting the terms of a pact between the two. Some time in the early Third Era, Mehrunes Dagon was defeated by the sorcerer Chimere Graegyn. Mehrunes Dagon was also behind the destruction of Ald Sotha, where he destroyed House Sotha. Dagon was defeated by the god-like Almalexia and Sotha Sil, but not before he destroyed the entire city and devoured its populace. The most famous of Dagon's invasions of Morrowind is certainly the attack on the capital city of Mournhold at the end of the First Era. He invaded Tamriel relentlessly from the First Era onward. The common reasoning behind his many plots is his belief that Tamriel is in fact a plane of Oblivion which is rightly his. Mehrunes Dagon is the foe of all mortal races, and has attempted to conquer the physical world Nirn many times. Mehrunes Dagon's spheres are destruction, change, revolution, energy, and ambition.

Oblivion servant of the dawn