Apotheosis is a rare process by which a mortal ascends into godhood. For example, Tiber Septim, who became the god Talos. Another example is Reman Cyrodiil, who later became worshipped in some sectors of Tamriel as the god Reman. A more famous example is the Tribunal Temple in Morrowind. In The Elder Scrolls IV: Shivering Isles, it may even be possible for the main character to achieve this process, as Jyggalag says that you will grow into this role.