Legion of Super-Heroes Vol. 1: Millennium

"Welcome to the 31st century! Inspired by the acts of and lessons learned from the greatest heroes of all time, the Legion of Super-Heroes have gathered together to stop a galaxy from repeating its past mistakes.... Why have the Legion of Super-Heroes broken the cardinal rule of the United Planets and inducted Jon Kent, a.k.a. Superboy, into the Legion? What are they hiding? And what does it have to do with Aquaman's long-lost trident?"--