And then it started like a guilty thing

Upon a fearful summons

what is the simile comparing "it" to?

A. a fearful summons. B. the feeling of dead. C. a guilty person. D. a court summons

B.

"it" refers to a pronoun, specific for animals or subjects, so C. wouldn't be an option.

And "summon" in meaning of "request someone to present" in this sentence, could be put like this:

when the fearful summons going into someone's ear (we don't know who), it trigger the person to have guilty feeling and also the fear of possibly dying.