Octavia is a former soldier and aristocrat of the Holy Empire, she now serves under Arawn as one of his many wives after a blunt incident.
When Arthur sent the men to put the crate, where Octavia was tied and put inside by her masters in the Holy Empire. She untied herself, jump out of the crate and tried to assassinate Arawn, but failed. Arawn later released her, but then retract the promise after knowing that her return to the Holy Empire will only mean her own doom.
Arawn, without the knowledge of the customs of the Holy Empire, grabbed her hand, wanting her to stay by his side - which she thought he was proposing to her. This custom in the Holy Empire means a proposal of marriage if you are holding an unmarried woman's hand.
This however, was different in the anime. Octavia was trapped in one of the crates until Lydia came along to remind her about their last meeting when she defeated her in a duel during the past. When the crate she was in has reached Avalon Castle, Arawn demands her to come out from hiding. She challenged him but he refused to fight someone who doesn’t have the will to live. Octavia later fainted because of her injury on her hip. Riannon nursed her.
Arthur, who is under Arawn’s order to know her character, later challenged her. She later swore by her sword that she will remain here as an independent female swordsman as well as sharing the fate of everyone who lived in Avalon Castle. In the same episode that all this has happened, she told Arthur that she was an aristocrat but her family was murdered because of her father’s rebellion against the Holy Empire. She inherited her elder brother's sword.
After discovering the Red Coral that Morgan was searching for, Octavia has two small pieces made with their names on as necklaces. Octavia kept Morgans while Morgan was given Octavia's, as a sign of their friendship.
During her early stay in Avalon Castle, she volunteered to teach 2 children, Elyr and Conale swordsmanship along with reading and writing.