The inquisitor of the Inner Sanctum like all the Black Crosses before him, Olier travelled al around the world to keep an eye on the Grand Masters of the various Rites, to verify that they stayed in line with the Templar Code and if necessary to eradicate any corrupted Templars he could find. His secondary mission was also to track Pieces of Eden for the Inner Sanctum.
Sometime before 1805, Olier was sent to Tripoli to infiltrate the palace of Sultan Selim III and investigate the Koh-i-Noor, but was captured and imprisoned. Believed dead, a new Black Cross, Solomon Bolden, was appointed, who eventually discovered clues about Tavis' survival and presence in Tripoli. However, Bolden was killed by the Sultan's men and his travel companion, Jan van der Graff, whom Selim believed to be another Templar infiltrator, was put in Tavier's cell.
During the three following years, the Black Cross took van der Graff as his student, teaching him the Templar tenets. However, on July 29, 1808, Olier sacrificed himself to allow van der Graff to escape and to retrieve the Koh-i-Noor before the Assassin Brotherhood.