Tenebrous of Darkness Between is a an entity of great power in the Marvel Universe. Tenebrous' power stems from The Crunch, a wall of energy that marks the very edge of the Universe, which one could see it expanding ever outward. Tenebrous was one of the Proemial Gods and existed when the universe was very young. Along with Aegis, the Lady of All Sorrows, he destroyed all of the Chaos Mites that were created by Diableri of Chaos.
Tenebrous was one of few Proemial Gods to be very loyal to Diableri's cause of remaking the universe in his own image. This battle eventually brought them to Galactus. Tenebrous and Aegis were the only Proemial Gods aside from Antiphon the Overseer, who decided to remain a neutral party in this conflict, that survived this battle and were imprisoned by Galactus near The Crunch.