Synopsis
In Infinity Crusade #4 Adam Warlock entered Soul World inside his Soul Gem to seek out his 'bad' side Magus who he'd exiled there (at the end of the Infinity War event). At the end of that issue he found him.
Magus knows that Adam longs to live in this paradise but he's needed in the real world. He graciously offers to grant Adam his wish by killing him, but neither of them know whether that could happen here. All the other souls in Soul World live together in harmony, even previous enemies, and they all appear to have their old bodies even though they they are truly only spirits. Magus too appears as normal but he is unique. Because he is but a fragment of Warlock he has no soul and cannot be seen, heard or felt by the other denizens. This is effectively solitary confinement. But now he tries an experiment by hitting Adam, and it works. Adam at least can see, hear and feel him.
Magus confirms that he is aware that Adam's 'good' side Goddess is causing trouble in the real world. When Warlock was temporarily a 'god' (with the power of the 6 Infinity Gems at the end of the Infinity Gauntlet event) he had expelled both his bad and good sides in order to be ruled by pure reason. And he never got them back when he gave up 5 of the 6 Gems. His bad side became this version of the Magus and threatened the universe in the Infinity War event. Now his good side has become the Goddess and is an even worse threat. Magus also confirms that he like Adam has worked out what Goddess' endgame is, but neither of them is going to enlighten us readers.
Adam says he's come here to enlist Magus' help against her because he's not sure he can succeed alone. While having no good or bad side does allow him a clearer perspective he finds that it limits his drive, his willpower. If Magus helps he promises to free him from Soul World, but only by reintegrating him into himself. Magus points out that this might cause Warlock to eventually turn into *him*, as it did in a parallel timeline that Adam stopped from happening (in Jim Starlin's 1st run of Warlock tales in Strange Tales and Adam's own series). Adam says that the danger posed by Goddess is worth that risk.
Magus replies that he doesn't care about the universe, and his hatred for Warlock is far greater than that for his Soul World prison. But he will go back to reality to oppose Goddess but he'll do it alone ... after he's killed Adam here so that he can take over his body in the real world.
So Magus attacks and the pair exchange blows until the bad guy lifts a huge boulder into the air and drops it on his foe so that only the end of his cloak is visible. He takes time to gloat until cloakless Warlock taps him on the shoulder and proceeds to pummel him into submission. But Adam's staff was also broken by the boulder and Magus falls near to the headless shaft. He picks that up and the ends glow with strange energy as he wields it against its owner. Warlock ducks and dives and jabs until he is able to wrest the staff from his grasp. With a couple more blows Magus is down and Adam's staff is whole again. But he discards it and the pair meet to fight mano-a-mano again until Magus finally gives in.
Adam retrieves his cloak and staff and prepares to leave Soul World. Magus sneers that he still hasn't a chance against Goddess and her collection of Cosmic Containment Units (or Cosmic Cubes). But Warlock says he has allies out there. And also this fight has convinced him that he *does* have the willpower to succeed. He is a complete being but Magus is only a shade.