Nebulon in a member of an alien race UL’lula’ns. The people of this race were water breathing, non humanoids, they had six tentacles, finned and they apparently used up all their planets resources. To fix this situation the high tribunal of Ul’lula’n they dispatched some of their people to locate a suitable planet with appropriate minerals to save their race. Nebulon posing vast biosphere tapping power was able to take other forms. He then changed to a glistening golden humanoid form which neared star systems with humanoid populations. He wasn't very good at prospecting though.
He eventually stumbled into Hyperion of the Sinister Squad imprisoned in a glass sphere created by Thor floating in space. Nebulon rescued him and told him about his mission. With Hyperion eager for vengeance against the people of Earth e offered to let Nebulon have earth. Hyperion although wasn’t aware of Nebulon's true form. When they got to Earth Hyperion had Nebulon reorganise Hyperion’s one time comrades. Nebulon's wish was to take over the world and put it underwater. The Sinister Squad, after hearing this, pulled together and built a laser cannon capable of melting the Earth's ice caps and plunging most of it into the sea with increased sea levels. However, one member wasn't wiling to help out and took this opportunity to call for help, this being Nighthawk. He then contacted the Defenders and told them about the situation. The defenders then went to the North Pole getting into a battle with the Squadron Sinister. Nebulon during this battle expanded too much energy showing his true form- a sight that even dismayed his allies. Nighthawk took this time of confusion to take the laser cannon power and direct it at Nebulon and in his weakened state he seemly imploded, taking three members of the Squadron Sinister with him. In actuality Nebulon had dispatched himself to the aquatic extra dimensional world called Zaar. The place had been inhabited by some race of philosophers called Ludberities.
The Ludberities then explain to Nebulon their philosophy and some unknown reason, Nebulon took it to heart. He abandoned his current mission and undertook a new one. This time it was saving the being of earth from innate foibles. He then returned to Earth in a new form as a less imposing human guise. He then started a movement called the celestial mind control. Its purpose was to liberate the powers of a human mind, through in reality it robbed the people participating of their free will and turned them into puppets. Eventually it spread around the world and the Avengers became aware of it. They decided they had to thwart Nebulon, and he was forced to put some of the Defenders in a whole other dimension while his movement went world wide. As well as this, there was a group called the Headman who were a group of renegade scientists with their own scheme to gain world wide political power. Eventually Nebulon and the Headman had found themselves working at cross purposes. Eventually after a few months the Defenders found a way to expose the Headman’s political machinations and convince Nebulon it was a hopeless task to try and force humanity to better itself. Eventually the tribunal of Ul’lula learned of Nebulon's interference with Earth’s culture and him abandoning his mission he had been convicted to death.
But before he was taken captive he fled to Earth's Ocean and took the form of Dorma, the deceased wife of Namor the Submariner. Convincing the Atlanteans that Dorma had survived, he used her popularity to gain control and tell them to launch and attack on London. The defenders eventually got involved since Namor was also a part of them and later on a Ul’lula starcraft appeared and captured Nebulon. It then stripped him of half his power. The tribunal then suggested to Nebulon that he commit suicide as this was the only honourable alternative for disgrace in his culture but Nebulon only turned it down. Later on Nebulon's wife Supernalia found out about his dishonor and went to earth to force him to take this honorable action. In the meantime though Nebulon inveigled his way into ranks of the Avengers but in reality he really wanted to siphon the power which he had lost. On Supernalias end to battle her husband and his new powerful allies she decided to join his foes the Defenders, eventually leading to the two groups being manipulated into fighting. By the time Nebulon's motives were found out, the hero’s energies were being drained. Supernalia then thought to herself that what she had been doing was a violation of her people's ethics and decided that she must commit suicide. Nebulon then found out and while trying to stop her fell victim to the same energy draining ray, killing his wife and himself, stating that this was the most honourable way to go.
Nebulon would later return half alive and half dead, controlling the mind of a powerful Celestial. It took the full force of 3 out of the 4 original Defenders to finally put him to rest.
Nebulon was created by Len Wein and Sal Buscema for use in Marvel comics. The characters first appearance is in Defenders #13 which was released in May of 1974.
Nebulon's full strength was unknown as it was never demonstrated. This is due to him being in his humanoid form or another disguise for most of his appearances.
In his humanoid form he drew upon the biospheric energy of planets. He could manipulate the energy to many different effects, such as making spheres, shields, or energy bolts. He could also fire a concussive blast that was capable of staggering the Hulk. He also had the ability to teleport across the surface of planets or between dimensions. Nebulon also was able to shape change to any form although the transformation process was so strenuous, Nebulon did not do it often. His power were derived from the energy’s of a world so it stopped him from interstellar teleportation and if left away from a world long enough his powers would drop to that of a ordinary human.
Also the Ul’lula weren’t as adept to shape shifting as Skrulls nor could they change as fast as them or make as a close facsimile of another being. Lastly Nebulon was apparently more gifted at this ability then the average Ul’lula. It was stated that his humanoid form was "less than half" as powerful as his real Ul'lula form.