Castus Arterius

Castus Arterius, along with his brother Pallix Arterius, was one of the twin sons of Quinteia Arterius, the infamous rebel biotic who became the Hierarchy's first cabalist at the culmination of the Unification War. After his mother's incarceration, he and his brother were raised by Aurelion Aurelos, as per his agreement with Quinteia - her sons' safety in exchange for her freedom. Formally adopted by Aurelion, they were styled as his 'sons' and considered to be a part of the Imperial Family.

Whereas Pallix grew to be the model son, who would one day succeed Aurelion as the first Primarch of Palaven, Castus became a man who was deeply troubled by his life experiences. The loss of his mother distressed him greatly and he began to resent Aurelion for taking her from him. He experienced night terrors about the Burning of Moesia, where Aurelion had ordered the destruction of his home and he, as a boy of just six, had witnessed death on a mass scale. Disillusioned with his life and unable to come to terms with his past, Castus became aimless and apathetic, not caring for anything other than his own hurt.

The only person Castus ever showed any genuine kindness towards, other than his brother, was his adoptive sister, Rea Aurix, Aurelion's eldest illegitimate child. He became completely enamoured with her and the pair began a relationship in secret. But when Aurelion decided that Rea would marry Pallix for political reasons, Castus was livid. He demanded that Rea refuse to obey her father's orders and elope with him instead, citing their love for each other being more important than politics. But Rea, unable to bring herself to defy her father, went along with his decision, marrying Pallix albeit unhappily. Castus felt hurt beyond measure, forced to endure the sight of the woman he loved being given away to his brother, who didn't even think of her romantically. His resentment of Aurelion only grew and festered into an absolute loathing for the man, and he began to fantasise about destroying him and his empire.

Castus attempted to continue his love affair with Rea in secret, even siring an illegitimate daughter with her named Elia Arterius, but was forced to pretend Elia was the daughter of his brother to protect Rea's public image. Unable to cope and feeling like everything was being taken away from him, he abruptly ended his relationship with Rea and married Teresa Kandros on a rebound, a woman he didn't even love, without first seeking permission from Aurelion. Aurelion was forced to exile Castus and his wife to Thracia to maintain political neutrality. Castus blamed Aurelion for taking the only woman he had ever loved away from him, along with his daughter who, by rights, he should have been allowed openly recognise as his offspring.

In exile Castus stewed in his hatred. He quickly had a son with Teresa, whom he named Quintus Arterius in honour of his late mother, but the pair of them did not get on, with Castus routinely bulling her and threatening to take Quintus away if she didn't obey him. The marriage, doomed from the start, quickly broke down; Castus divorced Teresa only a couple of years after their wedding. He forcibly removed Quintus from Teresa's side and returned to Palaven, again without permission from Aurelion. There he threatened to reveal the truth of Elia's parentage and take her away from Pallix and Rea, to spite Aurelion for "ruining his life" and "taking everything from [him]". When Aurelion peacefully attempted to stop him, Castus flew into a fit of rage and attempted to kill his adoptive father. Aurelion was forced to kill him in self-defence. As he lay dying, Aurelion cradled him in his arms and told him “I am sorry, my son.” Castus responded by spitting blood into Aurelion's face and whispering “I am not your son. I never was... ” before dying.

Aurelion suppressed all information of Elia's true parentage and had Castus buried with all due honours as a member of the Imperial Family, both to protect his reign and to allow Castus some dignity in death. Castus was buried in what would become the Aurelian Funerary Palace, in a tomb purposeful built for him. Several decades later, his brother Pallix and wife Rea would be laid to rest beside him. Elia would never learn of her true parentage, living her entire life believing Pallix was her true father. Quintus was promptly returned to Teresa, who raised him alone on Thracia. She would never remarry, too scarred by her experience of married life with Castus to risk it a second time. In time, Aurelion would formally recognise Quintus as a member of the Imperial Family, welcoming him to court and granting him permission to wear Tyrian purple.

Through Elia, Castus is secretly the forebear of Desolas Arterius II and all his descendants. Through his legitimate son, Quintus, he was the founder of the Thracian line of House Arterius, which died out in the late 8th Century CE during the Krogan Rebellions.

Castus has become something of a cautionary tale for turians, his legacy being the often harmful stereotype of House Arterius' moral duality. While his twin brother is universally praised for his loyalty to Aurelion and selfless duty to the empire, Castus tried to destroy both of these things from within to serve his own desires. Thus, the stereotype that in every Arterius exists the potential for either great selflessness or violent rebellion exists. It is for this reason that they are often not trusted by others until they have proven themselves.