In another life, a strange turn of fate occurred. Sarivoka, adopted daughter of Reiltar, was the younger babe, while Karevas, the older boy, was snatched up by Gorion.
Karevas Gorionson was tall, muscular and grew up in Candlekeep surrounded by tomes and tales of daring, high adventure and occasional lovers, as the greatest 'heroes' of the realms were wont.
Sarivoka, bastard of Reiltar, by contrast, was lithe, blue-eyed, and had some elven ancestry somewhere in a half-human grandparent. She grew up under the care of Winski Perorate. The arts of death were impressed upon her body and mind, but she eschewed the blade for the Art and the Power. Her studies were mostly academic, for a priestess of a dead god had little to draw upon, but her studies in the arcane excelled. Winski despaired, beating her with every lesson, and the way of steel became second nature for her. Her lithe figure became athletic, and her mind sharpened. Her studies in magic revolved around death and enchantment, and to her mentor's fury, illusion.
The day came when Sarivoka engaged in her final lesson, a lesson she took upon herself as a rite of passage. Aware of her heritage thanks to Winski, a former follower of the dead god Bhaal, lord of Murder, it seemed only fitting she sacrifice her master on the very alter he revealed her dark sire from.
It was pitifully easy, and she made sure his demise was slow, agonising. Sarivoka never revelled in pain, despite all of Winski's attempts to install sadism in her. She was aware of Winski's future lessons but she would engage in that particular rite of passage on her own terms, not on his. And so she cast her spell of silence from her lesser simulacrum; as Winski tried to twist that onyx ring of his, her true form, shrouded from sight, seized his arms, shackling first his wrists and then Rieltar's weapon of choice: a garotte.
Winski has taught her the sword, the Art, and the old ways of Bhaal's priesthood, but Rieltar taught her the price of infidelity, of betrayal that day when he executed his wife, her adopted mother.
Sarivoka sent a message to Reiltar with Winski's last breath. Then she raised his body as a ghast as his soul was sucked in the gem she prepared, and then she set it on a shelf. It was fitting, she decided.
Her childhood companion, Cythandria, was a fellow practitioner of the Art, and helped her with her first cantrip. They enjoyed a rivalry that pushed them to excel, to outdo the other. Cyth's favourite trick was to summon two ogres to her side; Sarivoka's favourite was her lesser simulacrum casting geas upon the guards, tricking them into agreeing to some mundane task.
Reiltar took over as her master in the Art, schooling her in economics and leadership. His lessons were demonstrated on his subordinates and those who failed him. Betrayal was also a failure. Sarivoka learnt this well. In time, she was assigned to study under Davaeron, a more experienced practitioner of the Art and master of the Cloakwood Mines. The Mines were the key to Rieltar's plan to supply the starved the Sword Coast with the iron it so desperately needed. It was a foolish plan, given how easily iron could be shipped into a port city but Sarivoka said nothing. Instead she bided her time.
She found herself under the tutelage of Tamoko, Rieltar's latest lover, a warrior from Kara-Tur. Cyth had also found her way to Rieltar's bed, Sarivoka suspected, but pushed aside her feelings. Power had always drawn Cyth; she was like a street drunk desperate for her next drop. None of them realised that Reiltar, Davaeron, even Cyth had fallen under her geas, that all the regional 'lords', Rieltar's associates, were hers.
She let them do as they wish, play their petty politics, recruit their mercenaries, assign her to this or that place. She even let them ruin the Seven Suns trading coster. And why? Because she was the daughter of the dead lord of Murder. Coin has its uses, a desperate city had its uses, but most of all? They would all murder themselves for her. She had Reiltar recruit mages and sign a contract of employment, a contract that would impress the denizens of the Nine Hells. A geas, of course. And through Cyth, Davaeron, Reiltar, and others, she cast her geas.
Sarivoka never set foot outside of Baldur's Gate after she arrived. She never went near her siblings. Instead, when the salvation to the Iron Crisis was announced, the entire city was purged by those 'loyal' to her, and then, they fell upon each other until only she was left.
In the wake of this, she felt her power increase and she raised the entire city as wraiths. Of course others came to investigate, drawn to it as Cyth was drawn to power.
They each succumbed, as the wraiths hid in the sewers and rose up at night. More and more were added to her ranks.
Eventually, events in Saradush came to a head, as Winski had foretold: her siblings vied for their sire's throne. Finally, only Sendai the drow stood, a practitioner of the Art and a priestess, much like herself. Believing that she had won, Sendai waited and waited... but the surrounding nations, notably the elves of Suldanessellar, could not tolerate a standing drow army on the surface and ambushed Sendai's beleaguered forces.
The drow succumbed to their brethren, and finally, Sarivoka made a journey to Candlekeep. Two geas later, and Karevas Gorionson and Imoen, whom Winski had identified as Bhaalspawn, worshipped at her feet and there, as the greatest house of knowledge burned, Sarivoka ascended as the new goddess of Murder.
It didn't take her long to set her host of wraiths against the libraries of the living, beginning a war against the other gods. She murdered many good books, their caretakers, and spread ignorance and superstition across the Realms. With that, she murdered reason; her agents accused mages and priests of being 'warlocks and witches' and the masses turned against them. It took a couple of generations but Sarivoka could afford to wait. Despite the best efforts of the other gods, she grew stronger and the people grew more and more ignorant until eventually the remnant clergy went into hiding... and with their dying faith, the gods faded. Eventually only Sarivoka remained as the principal deity, and she subsumed the profiles of the other gods. With every profile as her own, she turned her attention towards Ao, the tablets of fate, and smiled. Her time had come.