- Script
- Paul Levitz
- Pencils
- Joe Staton
- Inks
- Murphy Anderson
- Letters
- Ben Oda
- Editing
- Joe Orlando (original managing editor); Al Milgrom (original editor)
- Job Number
- J-5434
- Genre
- superhero
- Synopsis
- The Legion battle Mordru, who is revealed as the force behind the Dark Circle's plan to conqueror the Earth.
- Reprints
This story begins on inside front cover.
- Script
- Gerry Conway
- Pencils
- Joe Staton
- Inks
- Jack Abel (#249); Dave Hunt (#248)
- Letters
- Ben Oda
- Editing
- Jack C. Harris (original editor)
- Job Number
- J-5545; J-5545
- Genre
- superhero
- Characters
- Legion of Super-Heroes [Superboy; Colossal Boy (cameo); Light Lass (cameo); Brainiac 5; Sun Boy; Mon-El; Shadow Lass; Cosmic Boy; Lightning Lad; Saturn Girl; Phantom Girl]; R. J. Brande; Chemical Conqueror [Mantis Morlo]; Chemoid Monster
- Reprints
To merge the original two stories, the title page has been removed from the story in Superboy & the Legion of Super-Heroes #249.