Baron Apocalypse

Apocalypse expanded his domain greatly by waging war on his neighbors, conquering several domains and enslaving their barons as his own Horsemen.

Five years prior to the events that would lead to his own unmaking, Lord Doom forbade Apocalypse from waging war on his neighbors, causing him to crack down even harder on his own domain. Apocalypse's most bitter foes were the mutant rebels known as the X-Men.

Apocalypse eventually became suspicious of the remaining humans in his domain, led by the Friends of Humanity, suspecting they had some sort of weapon at their disposal. He also dispatched his Horsemen to locate Cypher.

His Horsemen eventually discovered that the humans had possession of the Legacy Virus, a disease that would kill all mutants and leave humans unharmed. His Elite Mutant Force launched an attack on the human settlement, and were engaged by the X-Men, who had also learned of the virus, and attempted to take it for themselves. Apocalypse personally intervened however, finding the canister and breaking it, unleashing the virus. Having come to believe that mutants had grown weak and unworthy after defeating humanity, Apocalypse believed that the virus would serve as a test to see who was truly fit to survive, as he believed that survival of the fittest meant having to endure continuous hardship to weed out the strong from the weak.

Apocalypse engaged the X-Men, but found that he himself had been infected with the virus. In disbelief that he was not worthy to survive, his own Horsemen turned on him, and being assaulted by the X-Men, his Horsemen, and the virus itself was enough to finally destroy Apocalypse, who had lost control of his powers of cellular cohesion, causing him to disintegrate into liquid.

After a rebellion against Doom's rule broke out across Battleworld, the events that led to Apocalypse's death and fall were undone, and he was brought back to life. He participated in a teleconference with Doom and Barons Pryor, Maestro, and Sinister regarding the Prophet. Apocalypse advised Doom to answer mercilessly and kill all the rebels, prompting Doom to order him and the other barons to put the rebellion down.

Later, Apocalypse and the others barons engaged the Prophet and his forces to defend God-Doom's capital of Doomstadt. Apocalypse and his forces arrived to turn the tide after Baron Sinister betrayed Doom's forces and killed Baron Pryor. The betrayal of the Thor Corps proved a deciding blow however, and Apocalypse was overwhelmed and knocked out. After Molecule Man, the source of Lord Doom's power, chose to give Doom's power to Mister Fantastic, Battleworld fell apart.