The In-Betweener represents the balance of all things opposite, such as life and death, cold and hot, or good and evil. He is an agent of Master Order and Lord Chaos. He was first seen when Adam Warlock abducted him and tried to turn him into a champion of good to fight against Thanos.
The In-Betweener sought to maintain balance by creating universal chaos. He began by manipulating Reed and Sue Richards into fighting amongst each other for the Infinity Gems, which they were searching for in order to save Galactus. He saw this as an opportunity to escape the Magick Realm and be the balance in an unbalanced universe. He formed an alliance with Trader, Astronomer and Possessor. He planned to kill Galactus. He sent the ill Galactus into his realm because they could not exist in the same realm together, betraying the Elders. When they questioned him he summoned Death and controlled her to kill them for he had the power. Death would not forget this insult.
The Silver Surfer called upon his creators and told him what had transpired. They arranged to control him if he could be returned to the realm. They also removed the other Elders that Galactus had consumed that were making him ill in the first place. They returned to their universe and Galactus battled the In-Betweener.
In-Betweener proved to be quite powerful, even outside his own universe. He seemed to be Galactus equal. When they started to fall into the Magick Realm, Silver Surfer, Nova and the Elders of the Universe helped push them in and lose his hold on Galactus. Order and Lord Chaos took control over the In-Betweener and imprisoned him within the Magick Realm. His place of imprisonment was in the Nexus of All Realities between the polarities of actuality. His prison was small but he still retained his powers, but could not escape. Demonic guards watched over him.
In-Betweener still possessed the soul gem from the conflict with Galactus. This attracted Thanos, who claimed he wished to free the In-Betweener for help against his current master, Death. Together they were able to free him but as soon as he was released his power left him. Thanos, of course, knew this all along and took the gem from him, leaving him to his master's fury.
Powers and Abilities
A massively powerful cosmic abstract entity, The In-Betweener thrives and is powered on duality and balance. The In-Betweener is the balance between Master Chaos and Lord Order. As such he can manipulate matter and energy on a massive scale. His strength, speed, knowledge are categorized as incalculable.