Final answer:
Dorian's relationship with Sybil Vane in 'The Picture of Dorian Gray' ends because Dorian values her acting talent over her as a person, and after her performance suffers due to her love for him, he rejects her. Devastated, Sybil takes her own life, which marks a significant point in Dorian's descent into moral decay.
Step-by-step explanation:
What caused Dorian's relationship with Sybil to end? In the novel 'The Picture of Dorian Gray' by Oscar Wilde, Dorian's relationship with Sybil Vane ends tragically due to a combination of his superficial values and her consequent loss of acting talent, which he believed was her only admirable attribute. When Dorian sees Sybil perform poorly on stage, believing her talent has vanished now that she has experienced true love for him, he coldly dismisses her, valuing her artistic ability over her as a person. Devastated by his rejection, Sybil takes her own life, thus ending their relationship in a final and absolute way.
The shock of Sybil's death and Dorian's initial lack of remorse highlight the theme of the superficiality and the degradation of his own soul, leading him deeper into a path of moral decay. This event marks a turning point in the novel and reflects Dorian's growing obsession with aesthetic beauty and pleasure over human connection and moral decency.