Superboy Vol. 1 #229

The Legion head to the homeworld of the Dark Circle to find Deregon and avenge Chemical King. Remember the five-cent phone call?

While some of the more powerful Legionnaires travel to space to search for Deregon and the Dark Circle, the three founding Legion of Super-Hero members, Saturn Girl, Lightning Lad and Cosmic Boy, learn that Deregon is actually on Earth. Knowing there isn’t a lot of time to get Deregon, they go after him and find him, with a fight ensuing. In the confusion of battle, Deregon falls into a pit of chemical wastes and is trapped, a fitting irony since he killed Chemical King of the Legionnaires.