The Moonchild
Sébastien grew up a very sweet child alongside his twin brother Jonathan, their father Joshua, and their very controlling mother, Francine. regardless, he loved his family, especially his ma... and oh boy, did she take advantage of this.
he would listen to whatever his ma told him, he was basically her puppet and emotional dumping grounds. Sébastien is very quick to latch onto people, and she made sure she was the only one who mattered in his life.
Francine
their biological father, Joshua Harley, was a private investigator and detective. Joshua tried very hard to get Sébastien away from Francine, but she would always pull him back. Joshua never got to helping the kids, because Francine convinced herself Joshua was cheating on her and hired a hit on him to have him buried when the kids were only ten.
later on during Jonathan and Sébastien's young adult years, Francine became involved with a shadow mafia by the name of La Populace and had previous relationships with their members. in fact, she dated a man by the name of Henri, who was an important figure among their ranks.
he presumably cheated on her, and being the horrible person she was, she hired a hit on him and had him buried just like she did her previous husband. La Populace wasn't stupid. they knew it was Francine who ordered the hit and sent their own on her.
The Doberman
it was on a night with a full moon when the assassin, donning a black robe and a dog mask. he came to their house and poor twenty year old Sébastien watched as the mysterious robbed figure beheaded her with his katana in their living room.
then he was gone, like a shadow into the moonlight.
Jonathan hid, being the smart one. but Sébastien? he was covered in his mother's blood as he held her body and wailed the night away until the police came.
the dog had come and he took away their mother, like a debt paid. after that night, Sébastien was never the same.
Repentance
a few months after the incident, Sébastien's childhood friend, Selena, and her adoptive father, Cailean, came to offer their condolences to the remaining Harley twins.
Cailean, emboldened by his daughter's insistence, wanted to offer the Harley twins a place to stay seeing they were struggling with rent. Selena of all people knew how hard it was for orphaned children to lose their parents and having to survive while grieving on their own. she and her twin, Helena went through the same thing after they'd lost their parents.
now, Sébastien wasn't stupid. he and his brother were the ones who the townsfolk came to whenever they needed to find answers. it was the thing he did best.
he knew for a fact that the man who stood before him was the very person who took his mother's life. he forced every bit of spite down into his stomach and put on a fake smile the best he could, accepting his offer with gratitude through venomed teeth. he played dumb, pretending otherwise.
and while everyone didn't give it a second thought, Jonathan knew that Sébastien's sweet demeanor was a lie. so Jonathan stayed behind, much to Sébastien's disappointment. he then would only see Sébastien during work hours.
Penumbra Covert
the two brothers had to get themselves together; their only parent was dead and they had to move on. Sébastien and Jonathan founded their own private investigation agency together, Penumbra Covert, using their biological father's old office. the two promised that they would get to the bottom of La Populace together. Sébastien for the sake of their mother, and Jonathan for the sake of Sébastien.
in reality, Jonathan knew that Francine was awful and it never sat right how she treated Sébastien, but all he wanted was closure for his twin brother. he would do anything if it meant Sébastien would find peace and move on.
Sébastien began taking some very sketchy requests behind Jonathan's back, being moved by the clients' stories of their affairs and dismays, as though he'd seen himself in them. he would blackmail cheaters and mistresses to literal death for the sake of revenge, not being different from what his mother was.
Jonathan confronted Sébastien and it resulted in a fight between the two twins. Jonathan revealed that Francine was the one who sent the hit on their father, Joshua, which Sébastien did not take well at all.
Sébastien walked away from that conflict and it was the last time Jonathan ever saw him for years. when Jonathan returned to the office and checked their home, Sébastien was nowhere to be seen. he'd taken nearly everything he deemed he owned and went his own way.
Lunar Church
after the fight the two brothers had, Sébastien headed to the Lunar Church. if he wanted change, he'd do it within the system. he tried very hard to forget about Jonathan, with questionable results.
during this time he stayed Selena, Helena and Cailean. he spent nearly six years working up the ranks, pulling strings and using his abilities in informational warfare to knock out competitors with the help of Selena and Helena behind Cailean's back, and even then Sébastien didn't tell them everything.
once Sébastien surpassed Cailean in rank within the Church and found an independent life, he no longer needed him. there was no reason to keep him alive, he could finally enact his revenge plot.
Cailean, the Doberman, would pay in full for killing his mother that one fateful night.
You're An Angel, I'm A Dog
the snowy landscape reflected the moonlight like white, sequined silk. quiet and serene before the storm.
Sébastien requested with urgency that Cailean meet with him on a quiet hill in view of the full moon. he made sure no one else caught whisper of it.
and so they talked. much to Cailean's confusion, Sébastien simply smiled at him and asked him if the moon looked beautiful. taken aback, Cailean demanded to know what Sébastien wanted from him in the dead of night.
he tried very hard to ignore the eerie smile Sébastien had - the very same smile Francine gave him when she first saw him in the living room that night. that knowing smile, as though she knew what he was there for...
...and Sébastien knew. he knew everything.
Cailean was too bewildered to properly react. he was blasted in the chest with a lunar beam, much stronger than he expected from someone as dainty and fragile looking as Sébastien. with his limbs and joints glassed from the lunar energy, he couldn't get back up again.
Sébastien wouldn't let him anyway. the child whose life Cailean ruined years ago quickly seized the opportunity and pinned him down, producing a contraption from his bag. it glittered in the pale light of the moon.
it was a lunar veil, capable of rewriting a person's mind and emotions entirely using their own fears. a forbidden device that was never meant to be used, scrapped and locked in the deepest parts of the dungeons. somehow, Sébastien dug it up from its prison.
then, Sébastien leaned in close. with a predatory look in his heavenly blue eyes and malice dripping from every word, he said...
I know you killed my mother.
those were the last words Cailean heard before the veil covered his vision. he would never be Cailean again. in Sébastien's eyes, death was merciful... he had other plans for Cailean.
You Believe Me Like A God
soon after, Sébastien was crowned Archbishop of the Church. his mental state, despite exacting his revenge, only deteriorated with grief and loneliness... and the lunar energy coursing through his veins would do what it does best - prey upon one's emotions.
what did he do with this newfound power? pull even more strings with his position to pass a law out of sheer rage that stated that all who practiced the shadow modus must be punished by death. no one would be hurt by the Acolytes ever again.
eventually, he did take down La Populace, indirectly with Tes' help. Sébastien never forgot about Tes even during the years they were apart.
Jonathan (or rather now, "Tes"), was practicing the shadow modus at the time. Sébastien knew this and a secondary purpose of passing that law was to draw Tes out of hiding and punish him for not being there for him when he needed it. he knew Tes was too smart to let himself get killed by some dumb cops.
oh, and he made gay marriage legal and abolished arranged marriage. Desmond, his childhood best friend, was very happy about that.
The Finale
eventually Sébastien snapped, his unhinged wrath reaching a breaking point. the only person who could convince him to step down was his brother, but unfortunately Tes was extremely hesistant and violently so.
it's a long, winded story, but the climax ended with Sébastien metaphorically tearing off the skin of the Moon and wearing it, trying to play god. it says something when Sébastien is literally so powerful that his mind overpowered a thing that is supposedly a deity.
Desmond had to convince Tes to face his younger twin, nearly getting killed in the process by an enraged Tes in his shadow form. Desmond, who also had a younger twin who he dearly loved, told Tes that he understood what it was like, and it wasn't just Sébastien's life at stake, but the entire world. Tes would soon come back after a cigarette to help talk down Sébastien from his power trip.
if it weren't for Tes, the mob would've had Sébastien's head on a pike. can you blame them after all he'd done? but Tes wouldn't let that happen. he disappeared with a heavily wounded Sébastien into the darkness, and that was the last time the general public has ever seen the Archbishop.