The first example of judgment is the angels when they sinned. The common Jewish tradition was that "the sons of God" in Genesis 6:1–5 (understood as angels) had sexual relations with women. As a result, God judged them at that time (see 1 Enoch 6–10; compare 1 Peter 3:19–20; Jude 1:6).
in chains of darkness: This phrase reflects a common ancient description of the underworld. It is probably a metaphor that pictures a place of deep darkness and confinement.