# did not spare

"did not refrain from punishing" or "punished"

# but delivered them into hell

"but threw them down into hell" or "but sent them to hell"

# to be kept in chains of darkness

Possible meanings are 1) "in chains in a very dark place" or 2) "in darkness that imprisons them like chains." Alternate translation: "where he keeps them in chains of darkness”

# until the judgment

This refers to the day of judgment when God will judge every person.