Why would I use an em dash instead of a comma to punctuate nonessential information?

Read the excerpt from chapter 18 in frankenstein. alas! to me the idea of an immediate union with my elizabeth was one of horror and dismay. i was bound by a solemn promise which i had not yet fulfilled and dared not break, or if i did, what manifold miseries might not impend over me and my devoted family! could i enter into a festival with this deadly weight yet hanging round my neck and bowing me to the ground? i must perform my engagement and let the monster depart with his mate before i allowed myself to enjoy the delight of a union from which i expected peace. examine this excerpt to analyze the way the author’s choice of words adds to the meaning and impacts the tone of this portion of frankenstein. what does victor mean when he talks about “this deadly weight yet hanging round my neck and bowing me to the ground”? how do these words affect the tone at this point in the story? use examples and evidence from the text to support your analysis. frankenstein chapter 18