Thyriellentha was a capable and friendly woman, but power-hungry, though only with legal methods and becoming petty and grasping. She had very strict standards for her subordinates. Thyriellentha cut all dealings with her family when her grandfather chose her cousin over her as heir.
Thyriellentha was born in the noble house of Snome. However, she distanced herself from the family when her grandfather Lord Arrabas Snome picked as his heir her cousin Dandobar Snome. Circa 1362 DR, she ascended to the position of leader of the watch-wizard contingent of the City Watch and commanded them efficiently. In the meantime, her cousin Dandobar chose her as his own heir, but this did not repair the fracture within her family.