It is unclear whether Magnum had superhuman abilities since birth, gained them via mutation somehow, or whether he was just initially very tough, though not superhumanly so.
Moses Magnum was born in Ethiopia, fifteen years before its invasion by Italy. At the time of the invasion, Magnum became fascinated with weapons and joined Italy's leader against his own people.
Magnum became a naturalized citizen of the United States of America.
At some point he became the head of the DRC, a weapons manufacturer. Magnum was hired by an unspecified government to test a devastating biochemical gas on people. His men began kidnapping people around the world; these people were taken to Magnum's compound in South America, where helicopter would drop the gas on them.
Amongst those slain by Magnum's toxic gas testing were the family of Thomas Sheridan.
The Punisher and Spider-Man stormed DRC to stop Magnum's gas experimentation. As intended, Spider-Man was captured and brought to Magnum's testing compound, where the Punisher met him, and the two proceeded to take apart the compound and Magnum's security. Spider-Man confronted Magnum himself, and was nearly overpowered, but the Punisher then shot a canister of Magnum's gas and the two heroes trapped Magnum in the chamber with the leaking gas. They returned to the US, leaving Magnum for dead.
Protecting himself with a self-contained anti-gas body suit, Magnum survived and escaped, swearing vengeance.
Hoping to recoup his substantial losses, Magnum initiated a mining operation on the island of Katsyu Shima, trying to tap the mineral and energy potential of the Earth's magma core. Samantha Sheridan, a geophysicist working as an environmental consultant on the Alaska pipeline, detected a hairline fault connecting the Alaskan and Japanese fault systems, which in turn made up major elements of the Pacific Rim. She predicted that Magnum's laser drill would, upon blasting through to the Earth's core, tear the Katsyu Fault wide open, which would topple the Pacific Rim like a line of dominos, triggering earthquakes along the Japanese Fault, the Alaskan San Andreas Fault, etc.
Magnum sought Samantha Sheridan to assist him in controlling the laser drill's effects.
Unbeknownst by Magnum, his agent Sakura was loyal to a mysterious Council, who wished Samantha Sheridan dead for reasons of their own.
Amanda Sheridan, grandmother of Thomas, sought out the Punisher to kill Magnum, but found him unavailable. She sent other agents after Magnum, but they all disappeared.
Amanda Sheridan hired Power Man to kill Moses Magnum, as well as to protect her great-granddaughter, Samantha, whom she believed Magnum intended to abduct to use in his project. Cage agreed to protect Samantha and to stop Magnum and his plot, but refused to kill him. Amanda sent him to Tokyo, Japan, where he met up with Samantha.
Magnum's agents ambushed Samantha Sheridan. Power Man was on hand to to fight them off, but he was then struck from behind by Magnum himself, who knocked him to the ground and incapacitated both Cage and Samantha with some sleep gas. Magnum and his men loaded the two in their plane to Katsyu Shima. Upon awakening, Cage overheard Sakura speaking through a hidden wrist comlink to the Council, who ordered him to slay Sheridan immediately. Though chained, Cage assaulted Sakura, stopping him from killing Sheridan. However, Magnum then opened a door below Cage and Sakura—whom Magnum had suspected of treachery, which Cage confirmed, dropping them both out of the plane.
Cage survived the fall and broke Samantha out of her prison cell, after which she led him Magnum's laser drill. They were discovered by Magnum and his men, who began firing upon them. Cage took out Magnum's men and then confronted Magnum himself. Cage eventually managed to overpower Magnum, who fled, returning with a laser to kill him. However, a massive earthquake then occurred, bringing the facility down upon their ears. Cage fled with Sheridan, while Magnum fell down the hole below his laser drill.
As Magnum fell towards certain death, he suddenly found himself restrained in a chamber of the immortal mutant Apocalypse, who offered him power and his life if he agreed to serve him, with the alternate to being returned to falling down the drill pit if he refused. Magnum agreed to serve Apocalypse in his efforts to cause chaos and strife, thus strengthening humanity in his eyes. Apocalypse apparently granted Magnum the ability to generate concussive force and seismic tremors.
Magnum purchased several Mandroids.
They who wield Power supplied technology to Moses Magnum, which amplified his Apocalypse-granted power. Magnum set up a base in a small group of volcano islets in the Kuril Chain (some distance from Japan. Magnum sent a message to the Agarashima, a port of the Japanese isle of Honshu, stating that it would be destroyed at 8:00 AM. He then used his "Magnum Force" power to disrupt the fault lines beneath the Agarashima, causing massive earthquakes that caused fuel explosions, resulting in a devastating firestorm.
When Sunfire and the X-Men opposed Magnum's plans, he sent the Mandroids against them. The heroes eventually overpowered the Mandroids, at which point Magnum projected a hologram of himself, issuing an ultimatum to the prime minister of Japan: They had 24 hours to acclaim Magnum sole, absolute ruler of Japan, or he would sink the entire nation.
The X-Men and Sunfire assaulted Magnum's base on several levels. Magnum held his own against the combined power of Colossus, Cyclops, Sunfire, and Wolverine, after which he unleashed more Mandroids against them while he prepared to fulfill his threat to destroy Japan if attacked. Entering his amplifier, Magnum directed his full power at Japan, but found it countered by the sonic force of the X-Men's Banshee. In a fierce struggle of wills and power, Banshee successfully contained Magnum's force, which shattered Magnum's volcano base. For a long time, Banshee lost the use of his power due to the injuries in his vocal cords from this massive strain.
High-Tech broke into Magnum Munitions and stole a computer disc containing files on the use of prosthetics, escaping from Magnum's agent, Mr. Lawson in the process. Magnum sent Lawson to retrieve the information, which he did via tracing a signal released from the file once opened at Stark Prosthetics by Curtiss Carr, High-Tech's true identity. Information in the file also attracted the attention of Deathlok (Michael Collins), who assisted High-Tech in fighting off Lawson, who attacked them in one of Magnum's massive Terrordome assault weapons.
Magnum instructed his employee Mr. Edgerton to have Lawson bailed out of prison and then killed. He insisted that all traces to Magnum Munitions be destroyed, and then demanded to learn everything there was to know about Deathlok.
Magnum appeared before the board at AIM world headquarters, requesting they withdraw their bid for a defense contract so that Magnum Munitions could obtain it. When they refused, he generated an earthquake that collapsed the building, killing those within it and destroying their factory complex. With AIM now unable to fulfill the weapons contract, he knew that it would go over to him. He intended to use the money from the multi-billion dollar contract to outfit his army.
Magnum and his army took over the African nation of Canaan, usurping the power of its king, Baru, thus acquiring diplomatic immunity. He used the leftover money from contract to broaden Canaan's industrial base. He also naturalized an undetermined, but large, number of African-Americans as citizens of Canaan.
Magnum sent his agent, the Phreak, to steal a classified military file from Wakanda. The Phreak was foiled and the file preserved by Deathlok, who had been summoned to Wakanda by the Black Panther to help them with computer problems. Meanwhile, he sent another agent, armed with a Terrordome, to steal a paper file from Wakanda's security system. W'Kabi and the Black Panther managed to destroy the Terrordome and stop its operator, after which Deathlok revealed that he had traced Phreak to Canaan. Traveling to Canaan to discuss the matter with King Baru, they learned that he had been overthrown by Magnum, who slew the Terrordome operator for his failure. To avoid a diplomatic incident, the Panther and Deathlok left. Magnum sent another agent, Killjoy, to assassinate the Panther, to throw Wakanda into chaos so that he could implement his plans without its interference.
Magnum made a public speech, declaring Canaan the homeland of African-Americans, revealing that he had recruited a "Talented Tenth," the cream of Black America to pave the way for his plan.
Deathlok and the Black Panther defeated Killjoy, though they both received heavy injuries in the process.
Magnum appeared as a hologram before Deathlok, making an offer to join him in establishing the African-American homeland in Canaan and requesting his aid in assuring its economic independence by taking Wakanda's Vibranium mound. Deathlok refused, at which point Magnum sent a squadron of Terrordomes to assault Wakanda's capitol in an effort to take the Vibranium by force.
In the course of the ensuing battle, Deathlok confronted Magnum himself, defeating him after a short struggle. Without Magnum's leadership, the forces of Wakanda soon routed Magnum's armies.
Apocalypse confronted Magnum, punishing him for his failures by destabilizing his powers, so that he triggered earthquakes any time he contacted solid ground
Magnum's agents created the Evangeline, an immense floating resort registered out of Alberia. The Evangeline remained floating at all times to prevent Magnum's out of control powers from activating.
Magnum learned of an experimental Seismic Cannon, designed by Rand-Meachum to control and ameliorate the tectonic forces that control earthquakes. He made plans to steal this device in an effort to stabilize his powers.
The hero Triathalon learned of this plot.
Magnum's Magnum Shells hijacked a plane flying from Tierra Verde. Upon that plane was Silverclaw, whom the Magnum Shells coerced into following their commands by threatening to kill their hostages. The plane landed at Kennedy Airport.
The Magnum Shells succeeded in trapping the Avengers—who had arrived to oppose them—within a cage generated by their Powerpodium, at which point Magnum himself appeared via hologram. Before he could announce his demands, however, the hero Triathalon appeared and destroyed the podium, freeing the Avengers and dispersing Magnum's transmission signal. However, Magnum's agents used a Magnum Force weapon to shatter three buildings, forcing the Avengers to focus their efforts on saving the civilians, allowing them to escape with the Seismic Cannon.
After the Magnum Shells left, Silverclaw revealed she had been coerced into assisting the Magnum Shells.
Triathalon managed to stow away on the plane piloted by the Magnum Shells.
Triathalon led the Avengers and Silverclaw to the Evangeline.
As the Avengers and Silverclaw infiltrated the Evangeline, Magnum had his agents channel energy via the Seismic Cannon into himself. Magnum hoped to use the cannon as a weapon in a display of sheer destructive force that would impress Apocalypse, who would hopefully restabilize Magnum's powers. The Avengers attempted to stop him, but Magnum overpowered the lot of them. The Scarlet Witch managed to use her chaos magic to drain Magnum's power, until he flattened her with a piece of machinery. However, as she collapsed, Wonder Man arrived (at the time requiring her to channel his energies back to Earth), and the hero tackled Magnum off the Evangeline, landing above the shore of Martinique. Magnum's powers then began setting off a series of tremors, ultimately opening the ground below him, which then closed over after he fell into a deep hole.