As a child, in an attempt to prove that she was as capable as any male child, T'Priell set out into the desert known as "The Valley of the Seven Winds" to complete the traditionally male only Kahs-wan ritual. Early on her trek, she encountered a le-matya, a Vulcan predator. Her father, who had followed his daughter into the desert, found her just in time and stunned the creature with a phaser. The le-matya, however, recovered from the stun more quickly than anticipated and attacked the pair from behind. T'Priell saved herself and her father by initiating a mind meld with the creature, confusing the predator just long enough for them to escape.
In 2371, T'Priell was accepted at Starfleet Academy, but defered her entrance for a year in order to do an independent study project on the common origins of the galaxy's various vulcanoid species.
On an uncharted planetoid at the edge of known space, she encountered a Romulan scholar named N'Vat, and his students, Selke and Terek, who were there for similar reasons. N'Vat cared little for his governments politics, and suggested that they work together and T'Priell saw the logic in it. In the days that followed, T'Priell and Selke became good friends.
Upon the discovery of advanced technology at an ancient ruin, Terek revealed himself to be a member of the Romulan Tal Shiar, and claimed the technology in their name.
T'Priell, in a desperate attempt to keep the tech out of the Tal Shiar's hands, activated the excavation explosives in her backpack and hurled them toward the tech. The resulting explosion destroyed the technology and mortally wounded her as well.
Before she died, she entrusted her katra to Selke, who promised to return it Mount Seleya, on Vulcan.
Unfortunately, A Tal Shiar sub-commander named Thokol had a different idea, and utilizing Tal Shiar technology, bent the otherwise peaceful Selke to his will. He then surgically altered her to look like T'Priell and submerged her personality and allowed T'Priell's katra, unaware of her own violent death, to control the body and go on to Starfleet Academy as a deep-cover spy.
In 2372, "T'Priell" arrived at the Academy and was assigned to the Academy's Omega Squadron unit along with the Ferengi Nog, the Andorian Pava Ek'Noor sh'Aqabaa and the humans Matt Decker and Kamilah Goldstein under the command of Trill Commander Kyethn Zund.
"T'Priell" studied at the Academy for over a year, until the traditional sophomore Parent's Day at the Academy. T'Priell's parent's, who had not seen T'Priell since she left for her independent study project two years prior and already felt that something was wrong with their daughter, had their concerns intensified during their visit.
Two weeks later, Telark and T'Pen contacted Academy Commandant Andrea Brand, and informed her that they had come to the conclusion that, illogical as it seemed, the cadet known as "T'Priell" was not their daughter.
Telark and T'Pen's message to Brand tripped a flag that the Selke persona had unconsciously placed in the Academy's Communication system designed to warn her if her cover were blown. When this happened, the Selke persona (or rather the violent, brainwashed Selke persona) took control of the body, captured Omega Squad, and set her runabout's course for Thokol's location.
However, T'Priell had been in control for too long, and fought Selke for control. Eventually, the real Selke's personality came to the fore, and she assisted Omega Squad in their escape.
After escaping Thokol and the Tal Shiar, Selke/T'Priell was finally taken to Mt. Seleya so her katra could be removed, only to discover that it had been in place for too long and could not be removed. Furthermore, the battle for dominance between T'Priell and Selke was killing them both.
With the assistance of squad-mate Betazoid Edam Astrun (who had the highest telepathic rating ever recorded in his people) and Commander Zund (who, as a joined Trill, had plenty of experience with integrating personalities), helped the two personalities merge into a third, distinct personality, who chose to go by the name T'Priell. Following the integration, Telark and T'Pen accepted T'Priell as their daughter.
Starfleet allowed T'Priell to remain in the Academy. The new T'Priell, when in combat with Omega's Klingon rivals in First Cadre, fought with the efficiency of a Vulcan and the ruthlessness of a Romulan.