Akatosh, the Dragon God of Time, is the chief deity of the Nine Divines in the Elder Scrolls series. He is often considered to be the firstborn of all the divines and is frequently mentioned throughout the series.
Role
While he is often regarded as the deity responsible for the natural events that occur in Nirn, he is also known for causing "Dragon Breaks" as well. At least three of these have occur, with only two of them playing a role in the series' storylines.
In The Elder Scrolls II: Daggerfall, the second of these so called events was dubbed the "Warp of the West". It involved the constructing of the brass golem Numidium, although Akatosh, Mara, and Stendarr took full responsibility for the event.
In the Elder Scrolls IV: Oblivion, Akatosh appears at the very end of the game to confront Mehunes Dagon. As his name applies, he takes the form of a dragon and battles the evil deadric prince, which ends with Akatosh being victorious and expelling Mehunes Dagon back to Oblivion.
In The Elder Scrolls V: Skyrim, another one of the dragon break events occurs dubbed "The Time-Wound" where three legendary Nordic heroes sent Alduin in time in order to defeat him. Alduin is then sent to 4E 201, where the game line takes place.
It is also worth mentioning that some Nords believe that Alduin is Akatosh, although the World-Eater claims that he is the first-born of the said god.