After his initial defeat by the original Enforcers of Justice, the otherworldly tyrant known as the Overlord was trapped in a dimension of pure energy. He remained imprisoned there until alternative energy experiments by Dr. Albert Michaels at S.T.A.R. Labs in New York City accidentally made a connection to the dimension. Though insufficient to enable Overlord to escape, the connection was enough that the villain was able to use his willpower to influence and later take complete control of Dr. Michaels.
A lead researcher at S.T.A.R. Labs, it turned out that Albert Michaels led a secret double life as a senior member of the criminal gang known as SKULL, whom he supplied with high tech weaponry covertly acquired through S.T.A.R. Labs. Through his control of Michaels, Overlord now also had effective control of SKULL. Making further use of the technology at S.T.A.R. Labs the Overlord, still in control of Dr. Michaels, was able to open a portal to Otherworld and bring several of his Elite to Earth. The first to cross over was the scientist Styxx, followed shortly by the psychic vampire Mindshadow and later Overlord's chief soldier Horde.
Through SKULL the Overlord began consolidating other criminal gangs in Manhattan's Lower East Side. Many of these gang members were secretly sent over to New Jersey, where Styxx had set up a facility to convert them to Pseudo-Men, while more promising ones were given more senior positions within Overlord's forces on Earth. The first Thunderblade was one of the latter, being given his high-tech armor and sword by Styxx. Using technology looted from S.T.A.R. Labs, Styxx was able to construct a new containment body for the energy being known as Hellfurnace and summon the creature to Earth.
This activity went largely unnoticed, as the city's resident super-hero team Justice Inc. were distracted at the time. Some of the other scientists at S.T.A.R. Labs had become suspicious of Dr. Michaels' activities, but by the time they decided to do something about it, it was too late. Using Michaels' research as a starting point Styxx was finally able to devise a way to free his master from the energy dimension and Overlord was now able to physically manifest on Earth. With his arrival his forces immediately launched a series of attacks and swiftly seized control of the island of Manhattan.
In the initial wave of attacks, Justice Inc. along with their ally Galahad and a new vigilante calling herself Arclight, were forced to retreat into hiding. The attacks attracted outside attention and the Justice League attempted to intervene, but they were thwarted when Mindshadow was able to possess Superman. With the League's most powerful member under Overlord's control the heroes were driven out of the city and Styxx engineered a force field that surrounded Manhattan, keeping the heroes at bay.
Using nanotechnology, Overlord began quickly converting the S.T.A.R. Labs building into his new fortress. While this was happening his troops began taking the captured populace of Manhattan to conversion centers built in several locations across Manhattan where Styxx would start converting them into more Pseudo-Men troops. If completed this would add close to one million new soldiers to Overlord's army on Earth. With most of Earth's heroes blocked by the force field, the main threat to Overlord's plan was Justice Inc. and their allies, who had gone into hiding as Overlord's forces had taken control. Now Mindshadow, still possessing Superman, was scanning Manhattan trying to locate them.
For their part Justice Inc. had not been idle. In addition to Galahad and Arclight they had located other allies who had escaped detection or capture under the force field. These included several members of Ameriforce, the corporate super-team of the New Conglomerate, and the young metahumans who called themselves the Justice Subs. Time was not on their side, so the heroes had to act quickly before defeating Overlord and his forces became impossible. A plan of action was decided on; while their allies concentrated on taking out the Pseudo-Men conversion centers and other key enemy locations across Manhattan, Justice Inc. would go for Overlord's fortress at S.T.A.R. Labs to try and take out the force field, knowing that this would also involve confronting Overlord and many of his Elite.
Ameriforce, the Conglomerate, the Justice Subs, Galahad and Arclight attacked first, to deal with the conversion centers and confront Horde and the Pseudo-Men. With the bulk of Overlord's forces thus occupied, Justice Inc. struck at S.T.A.R. Labs. The team was soon engaged with Overlord and his Elite, and the odds of victory shrank the longer the fight lasted. The tide finally turned when Mindblade was able to release Superman from Mindshadow's possession. Now that the Man of Steel was free the tide of battle turned and he and Justice Inc. were able to defeat the invaders. With Overlord and the Elite out of the way Justice Inc. were able to disable the force field and the Justice League were able to get into the city to help defeat the rest of Overlord's forces and free Manhattan.