The death of Frankenstein’s wife is obviously very pivotal, and can be considered the final straw in his and the creature’s battle that takes Frankenstein from a respectable man with friends and family to a man with nothing to lose. This monologue is meant to be the creature coming to the conclusion that he will murder Elizabeth to bring down Frankenstein.
I was inspired by the scene where Frankenstein almost creates, then destroys, a mate for the creature. The creature is distraught after this, and I wanted to put that in words. He thinks an eye for an eye will be the best course of action. My monologue for the creature takes place immediately after that scene and right before the creature tells Frankenstein he will be with him on his wedding night. I was also inspired by the end where the creature recounts his sorrow and guilt for killing the people he had done away with to Walton. It showed he felt bad about hurting people, but felt he had to do those things to teach his creator a lesson. I tried to convey this much in the monologue.
I wanted to give the creature some time to explain himself that wasn’t at the end of the book. Since this story is told from Frankenstein’s point of view, we really only see/interact with the creature when he is with Walton, or his mortal enemy Frankenstein. This monologue gives the creature some time to shine on his own and be himself without someone to threaten or pander to.