The psalmist speaks of "terror" as if it were a spirit or fierce animal that could attack at night and so terrify people. AT: "things attacking you at night" (See: [[rc://en/ta/man/translate/figs-metonymy]])
"Arrow" here is a metonym for the people who shoot the arrows. AT: "people attacking you with arrows during the day" (See: [[rc://en/ta/man/translate/figs-metonymy]])