When he was young, Tyzack tried to rebel against the Zhentarim and killed a young cleric of Bane in a little temple north of Zhentil Keep. From then on, Tyzack lived in fear that someone would discover his secret.
Later, Tyzack joined the Zhentilar army and soon become the leader of the Company of the Scorpions. Furing the Time of Troubles, he and his men met the mortal Cyric, by that time starting his career in evil, and soon Cyric become the second-in-command of the company. All the previous bearers of the title had been killed by Tyzack's personal assassin 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.