Ren was a member of the Company of Scorpions and also Tyzack's personal assassin. His duty as assassin was usually to silence all members of the Company that discovered the captain's secret: in his youth, Tyzack has tried to rebel against the Zhentarim.
All changed when, during the Time of Troubles, the Company of the Scorpions met the mortal Cyric. Soon, Cyric become the second-in-command of the company. All the previous bearers of the title had been killed by Ren for discovering the captain's secret. In the end, during a rain of metal blades—a manifestation of the crazy magic of that time—Tyzack died, probably killed by Ren, who considered Cyric a better commander. Ren later explained Tyzack's secret to Cyric, and the two mocked the dead captain for his stupidity.