Legion of Super-Heroes #308 (1983) (High Grade)

The Legion of Super-Heroes track down Prophet to Khundia. They try to get some answers from him about a destroyed planetoid, but his only answer is that they need to be warned about an oncoming force. Prophet is extremely powerful and is able to deal with the Legion's attack with ease. Eventually, Prophet explains his origin and names the threat he is warning about: a being named Omen. As powerful as Prophet is, it appears that Omen will be much more powerful.