Lord Ariabert Tytania is one of the four dukes of the Tytania Clan in line to succeed Ajman Tytania as the next head. He was the duke in command at the Battle of Cerberus where Tytania suffered its first defeat in 200 years at the hands of Eurian commander Fan Hyulic.As rivals striving to be appointed as the next clan lord, Idris especially tries to take advantage of Ariabert's failure, but with the help of Jouslain he manages to restore his name and remain in position. Ariabert and Jouslain's friendship is unique among the dukes of Tytania.
In the novels, Ariabart loses to Fan Hyulick twice but at least uses it as a motivation to change himself, beginning to acquire flexibility fitting a possible next clan head (hence, Ajman's mysterious remark in the anime about how he would have to thank Hyulick if Ariabart changed after the defeat gains meaning).
Later (after the end of the anime), Ariabart falls for Hyulick's clever tactical trick again in the Pony war and subsequently suffers a second defeat at the hands of Fan Hyulick, also sustaining an injury, although not life-threatening.
Following the second defeat, Ariabart tries to take responsibility by giving up his position and declaring his resignation from the 5 families council, but Jouslain protects him which rapidly deteriorates the situation with Idris to the level where even use of force becomes an option.
Ariabart and Jouslain are officially cousins (their mothers are sisters), but not only: they're also half-brothers, sharing the same father as Jouslain's father had a secret affair with Ariabart's mother (his wife's sister), which led to Ariabart and Jouslain being born in the same month.
He was shot by Zelfa Tytania on Ajman's orders who came to negotiate ceasfire with him.
