Only the remains, the skeleton, of Sinderion can be found in his Field Laboratory in Blackreach. He was searching for the very rare Crimson Nirnroot as his Field Journal explains. The Blackreach inhabitants got the better of the alchemist.
Sinderion was an Altmer master alchemist living in Skingrad, south-central Cyrodiil, at the time of the Oblivion Crisis (the end of the Third Era). He lived in the basement of a well-known tavern, The West Weald Inn. There, he maintained the most extensive and modern alchemical laboratory and shop known in the whole of the Tamrielic Empire.
Sinderion was known to have had contact with the Champion of Cyrodiil, who agreed to gather for him a massive amount of the herb known as Nirnroot. This water- and shoreline-inhabiting herb was known to be slowly disappearing from the landscape of Cyrodiil, but Sinderion had discovered from an old tome that it had potential magical properties.
The collaboration produced a supply of a rare potion, the Elixir of Exploration, formulated for dungeoneering types. He developed it in several different strengths, with varying powers according to the amount of Nirnroot extract.
Sinderion, being Altmer, was long-lived, and after the Oblivion Crisis and the self-sacrifice of the last Dragonborn Emperor, Martin Septim, began the search for a rare variety of Nirnroot said to have elusive alchemical properties, Crimson Nirnroot. He eventually found his way to a Dwemer ruin in Skyrim, known as Blackreach. There, he unfortunately perished, probably at the hands of his degenerate underground-elven cousins, the Falmer, shot by two dwarven arrows. His remains were discovered three hundred years after the end of the Third Era in an alchemical research station (Sinderion's Field Laboratory) he had established in a stone ruin in the depths of the Dwemer ruin.