The warring factions of the Rock People and the Crystal People from Mercury use Earth as a base for their conflict. The Justice League must bring peace to the warring factions before Earth ends up in the crossfire.
A criminal warlord named Rom-Nex uses a gravity device to attack Earth. The Justice League are warned in time by a rebel named Val-Kar.
A malevolent warlord named Mastermind lures the Justice League to a trap on a mammoth desert mesa so that they will not interfere in his plans to take over Earth.
