The enigmatic Sotha Sil is the least known member of the divine Tribunal of Dunmer Temple faith.
He was once the last of a dying Dunmer great house, but went on to become a great sorcerer in life, and discovered how to harness Kagrenac's Tools to steal power from the Heart of Lorkhan, making himself, along with Vivec and Almalexia, to be gods.
The wizard once traveled into Oblivion by way of the Dreaming Cavern, and made a pact with the more prominent Daedric Princes during the war between Morrowind and Cyrodiil. Though the exact terms of this pact is unknown, it was meant to insure that no amateurs could summon the daedra during that time.
However, this pact did fail when a Breton witch managed to summon Mehrunes Dagon to Mournhold, leading him to then lay waste to the city. Sotha Sil and Almalexia arrived too late to prevent this catastrophe, but were able to drive him back into Oblivion before the city had been completely destroyed.
Over time, the wizard disappeared from the public eye, retreating into his Clockwork City, and his experiments. Eventually, Sotha Sil completely cut himself off from the outside world, and was not heard of again until he was betrayed and killed by his old friend and ally, Almalexia.