Tieria seems rather stoic and distant, although also proud and arrogant. Constantly believing he has the best interests of Celestial Being in mind, he rarely acts out of impulse, and has little patience for the impertinent. To this end, he often clashes verbally with the other Gundam Meisters, as well as his “superior”, Sumeragi Lee Noriega, on topics ranging from insubordination to ideology. Tieria is often noted for being on an extremely high horse, looking down upon others. Tieria also shows an unnatural loyalty to Veda, the supercomputer of Celestial Being, which Tieria can directly interface with. This link between Tieria and Veda can explain Tieria’s holier-than-thou attitude, and his belief that he is a judge of the members of Celestial Being.Tieria is shown to also be rather intelligent, and capable of making competent snap decisions. His direct connection with Veda permits him to know more about Celestial Being than his fellow Meisters.
At the start of the series, he had an extremely rocky relationship with Setsuna; the former does not understand why the latter was chosen by Veda as a Gundam Meister, and believes Setsuna’s brash actions and random insubordination will breach the code of secrecy of Celestial Being. However, he eventually found more a common ground with Setsuna in their vehement dislike of Team Trinity, even going so far as to back him up when he decides to combat them; this unexpected move, along with the teamwork strategies used in the battle, surprises the rest of Celestial Being.
Recently, cracks in Tieria’s cold exterior have become prominent, showing a softer and more vulnerable side that contrasts greatly with the emotionless and superior Meister he seemed to be. After Lockon Stratos is injured protecting him from an enemy attack, Tieria displays a great amount of guilt and remorse. He angrily blames himself for Lockon’s injury, even going so far as to call himself unfit to be a Gundam Meister. Lockon comforts him, yet afterwards when Tieria regains his composure he reverts to his old habit of snapping at his comrades.
When UN Army forces attacked the Meisters, Tieria locked Lockon in his room to prevent him from entering the battle, saying to Allelujah that he will protect Lockon as he saved him. He becomes increasingly concerned when Lockon manages to join the fight, and later when he disappears chasing Ali Al-Saachez. Just like the others, he is seen crying when they realize Lockon has been killed.
Following the return of the three remaining Meisters to the Ptolemaios, Tieria takes his emotions out on Setsuna, blaming his being “slow” as the reason for Lockon’s death. Seeing this, Sumeragi breaks up the fight by promptly slapping Tieria across the face. Shortly afterwards, as Nadleeh is being repaired, he vows to Allelujah that he will fight back for Lockon’s sake, despite the former’s warning.
Soon after entering battle with the force of GN-X units plus Alejandro Corner’s mobile armour, Alvatore, Tieria activates Nadleeh’s Trans-Am system; however, he soon loses a limb and the Trans-Am is deactivated, leaving him vulnerable to the two GN-X units that attack him, one of them being piloted by Patrick Colasour. The two fire at each other simultaneously; while Tieria’s shot destroys the GN-X and disables Patrick, Nadleeh is reduced to a mere torso.
Tieria is last seen in the cockpit of the Nadleeh, struggling to eject his GN Drive before losing consciousness, saying he is “going to where Lockon is”.
However, Tieria is confirmed to appear in season 2, piloting the Seravee Gundam.