The Dark Urge. Bhaal's Maiden. 

A bhaalspawn, born directly of her father's flesh, but raised outside of his cult by an unknowing tiefling couple. They were the ones to name Kore, and they were the ones to instill an appreciation of music and a desire for true love into her. She always looked up to the sort of couple her parents were, after all. She would be lucky to find a love like theirs.

But good things can never remain, and when Kore turned nine, her urge awoke and murdered her parents. She was found quickly by the demonic butler, Sceleritas Fel, shortly after that, who carefully pried the crying child away from the bloodied bodies and took her to the Temple of Bhaal underneath Baldur's Gate. This is where Kore learned to wield her blades, how best to spill blood, and to take her Father's doctrine to heart--that all is ash and meat, and all are destined fall to her Father's blade, even herself. By the time that Kore takes over the temple, she has more than earned the role, leading her beloved bhaalists with perverted affection and using her flute to charm all her victims before slicing their throats. All in the name of her Father. All for His love. 

It's in this pursuit of His love that Kore finds herself allying with remaining chosen of the Dead Three, hatching a plan in the name of their gods to subjugate an Elder Brain and gain control over an army of mind flayers. Everything was going so perfectly... until she's sabotaged and defeated, a mind flayer's tadpole placed in her head to subdue her.

Without her memories, Kore wakes up on the nautiloid, unknowing of who she is... only aware of the urge in her head telling her to kill, kill, kill. And kill she does, at least for a short while. Until she discovers that maybe some good company, maybe helping people, feels better than spilling blood...