Supermann #7/1971

In "Fanger i de udødeliges verden," Superman, Robin, and two brothers from Hudson University are suddenly whisked to an alien world where they're trapped in a desperate struggle to survive. The planet's inhabitants, led by the enigmatic Lynvingen [Batman], rely on a machine that feeds on life force—using Superman as a living battery to sustain their immortality. With time running out and their captors unmoved by pleas, the group must find a way to outwit their alien jailers before their strength is drained.