Tarmel had a fiery temper and appeared to be at least slightly mentally imbalanced as he enjoyed committing arson. He nursed a strong grudge against his father.
Tarmel was raised with his legitimate brothers. As a youth, Tarmel engaged in thefts, arsons and brawls and was even rumored to have committed murders. His father, Rancelair soon grew tired of his antics and disowned him, stripping him of the right to use the family name.
Penniless and nameless, Tarmel attempted unsuccessfully to burn down the family stables in Suszail. When this failed, he journeyed to Sembia where he lived for months as a bandit in Sembia's forests. He accumulated enough gold to purchase weapons and a wagon to conceal them in and he traveled to the Illance summer home at Stag Well in Cormyr.
Tarmel attacked his father and the family guards and, although he killed many of the family's retainers, his father survived. Tarmel did manage to steal a small fortune from a cache the family had at Stag Well. Because his father was engaged in illicit meetings with other nobles at Stag Well, the incident was hushed up for weeks which allowed Tarmel to escape and he returned to Sembia a rich man.
After his return to Sembia he was secretly sponsored by other banished nobles who replenished his coin stash with money of their own. Tarmel mistakenly believed some god had taken an interest in his "just" cause and was responsible for the mysterious coin.