A sister of Sorath that loves and follows him protecting him while they look after Nietono no Shana.
Her full name is Aizen Tiriel, but she's called as "Aizenta Tiriel". She and Sorath are known as the "Aizen Siblings". She's Sorath's younger sister.
Although being younger than Sorath, she's more mature and only seeks to satisfy his brother. She just loves her brother and hates anyone who tortures him. She often kisses his brother, something that Shana finds disgusting. Even though she loves Sorath, she is a jealous person that doesn't hesitate to torture her brother, for example when Sorath mention "Hecate", she strangles him.
She has a blonde hair and blue eyes, and her appearance is like a little child (a loli). Despite her look, she has a kind of mighty and mature aura. She wears a pink sweet lolita dress, a hat that match her dress, and a pair of red shoes.
Her flame color is the same as Sorath, bright golden yellow flame.
Tiriel and Sorath come to Misaki City in order to search for Nietono no Shana, Shana's katana. They're escorted by Sydonay (Tiriel asked for his help). In the anime, their first appearance is when Sorath get caught by a group of gangster, and Tiriel come. Tiriel tells her brother to eat the gangsters, and Sorath eat them.
Tiriel then put a spell on a treasure tool called Orgel. The spell allows her to produce plants that follow her command, and even the plants are destroyed, they will regenerate themselves, as long as the Orgel's not desytroyed or moved. Then, Shana comes and fights her. She managed to capture Shana and take Nietono no Shana from her, but Yuji and Margery Daw were fast enough to save her in time. She hurts Sorath with Bluutsauger and releases a enormous flame that can kill both of the Aizen.
Tiriel and Sorath can survive from the attack, but it's revealed that it's because Tiriel sacrifices herself for Sorath, use most of her existence to heal Sorath and to escape from the attack. Margery Daw fights Sydonay, and Margery beats him, and he runs away when he sees that they begin to have the disadvantage in the fight.
Tiriel begins to disappear, and Shana destroys the Orgel along with her. She tells Sorath to do whatever he wants and she vanish. Sorath attacks Shana with Bluutsauger, but Shana tricks him by throwing Nietono no Shana. Sorath gets his attention distracted, and Shana kills him.
She's voiced by Yukari Tamura in Japanese and Jocelyne Loewen in English.