Complex sentence: Darklighters are primarily only a threat to whitelighters and witches, and have the task of furthering the spread of evil back to Hades, in part, by luring likely future whitelighters into selfish and evil behavior through seduction.
Split into simpler sentences: Darklighters are primarily only a threat to whitelighters and witches. They have the task of furthering the spread of evil back to Hades, in part, by luring likely future whitelighters into selfish and evil behavior through seduction.