And if the look frozen on his face in Tribunal is any indication, he may have died the most horribly.
Alamalexia claimed he didn't make a sound, though. Either she was lying, or delusional, or he had been frozen in a catatonic state for some time.
Judging by his emaciated looking forearms and the length of his fingernails, I'd guess he's been "plugged in to the matrix" for a good 12 months by the time Almalexia bashed his skull in with her spells and weapons. He may have had that look on his face for a long time, although it's not clear to me why he was wearing his war mask. (partially broken by Almalexia's attacks, the "powerful energies" that the Nerevarine writes about in his journal)
Or maybe he dealt with them so someone would remember him. All he left behind otherwise was a poorly designed clockwork city that only one person can visit and a minor army of easily beatable cyborgs. Might as well be remembered for scolding Nord children.
http://www.imperial-library.info/obscure_text/sotha_sil.shtml
Just a note on Sotha Sil my friends....
That was not the entire City. No indeed. It was Master Sil's main hall within his hidden city of Clockwork madness. Just as, outside of the pearly gates in Mournhold, exists a crawling area of numerous homes, citizens, and vendors. Sotha Sil is quite expanse and houses many more inhabitants. I have seen them in person, and my, what a sight! In the case of the Nerevarine, I hear tale that when he was teleported in by Almalexia, the machina lift door behind him was caved in. For whatever reason (did Almalexia do it or did Sotha Sil?), this barred him from venturing further. Where the Nerevarine actually was, is Sotha Sil's workshop/lair.
Think about it though.... if this were a city, who could possibly call this place home? More intelligent fabricant type inventions? I dare not tell, although I have seen it with mine own eyes. Perhaps one day, the location will be openly known, and visitors can venture forth into the Clockwork City entire.