The Question and Answer section for Iliad is a great resource to ask questions, find answers, and discuss the novel.
Apollo was responsible for the plague. He sent the plague to punish Agamemnon for claiming Chryseis as a prize of war. He wants her returned.
I'm not sure which story "vengeance" is related to. You will need to tell me which battle you are referring to.
Who do you mean by "prism"?