How do Sibyl and Basil's death have an impact on Dorian Gray in The Picture Of Dorian Gray?

This is complex. Dorian's comment that Sibyl's death seems "to be like simply a wonderful ending to a wonderful play" continues the theme of life imitating art. It also recalls Dorian's obsession with the characters that Sibyl portrayed. He became disappointed in her when she tried to be her own person, and rejected the falseness of playing a role. Now, her death has given Dorian the ability to once again view Sibyl as a character in a play. When Lord Henry encourages this interpretation of the tragedy, he ensures that Dorian passes the point of no return on his descent into immorality.