Tenebrous of Darkness Between is an entity of great power. Tenebrous' power stems from The Crunch, a wall of energy that marks the very edge of our Universe, which is constantly expanding 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.
Major Story Arcs
They remained there for centuries until the Annihilation Wave destroyed the prison, freeing them and other prisoners of Galactus including Fallen One, Galactus' first herald, and Kosmos the Maker, also known as the Beyonder. Tenebrous began draining the strength of Fallen One and with this newfound strength he and Aegis confronted and easily defeated Galactus and Silver Surfer.
Thanos arrived with a Chaos Mite on his shoulder who would not reveal how she survived all this time to Aegis and Tenebrous. Thanos began to drain to The Power Cosmic from Galactus and Silver Surfer and then handed both over to Annihilus . Some time later Tenebrous and Aegis returned to their old prison in hopes of finding other surviving Proemial Gods. All they could find was the rotting corpse of Antiphon the Overseer.
By this time the Silver Surfer and Galactus had escaped from Thanos and Silver Surfer found Tenebrous and Aegis at the ruins of the prison. Galactus soon arrived only to witness the Silver Surfer's impossible victory over both Tenebrous and Aegis. This marked the end of the last Proemial Gods.
Tenebrous returned from the dead years later protecting our Universe alongside Galactus, Aegis and The Prime Celestial Host from a massive assault vanguard from The Cancerverse that had been sent to clear the way for The Many-Angled Ones. He is believed to have either died or retreated from the front lines when The Galactus Engine started killing his allies, including Aegis, left and right. His true fate, however, remains unknown.
Powers and Abilities
Tenebrous possesses great and terrible cosmic power that rivals and perhaps even surpasses Galactus' own power, so it's assumed that he possesses very similar abilities of Galactus. Though he has been known to dabble in energy manipulation, Tenebrous apparently prefers using hand-to-hand combat when facing foes of equal height and power. He has displayed enough to seriously injury and almost kill the Silver Surfer. His super strength also proved too much for the Surfer and was able to go toe to toe with Galactus. He also possessed some form of energy absorption when he capture the Fallen One. When he returned him to Thanos, he was a withered body.
He can also grow in size, which isn't that uncommon trait amongst beings of his caliber. Though he has never been seen using it, evidence of this abilities existence was revealed in Thanos Imperative #1; where both he, Aegis and Galactus are seen standing equal in height to their 2000 foot tall Celestial allies.