Years ago, U.S. government mutant operative Kevin Tremain was sent into northern China to neutralize the perceived threat posed by the Chinese ultra-nationalist the Mandarin. Betrayed by his agency, Tremain was captured by the Mandarin, who intended to use Tremain as the template for an army of mutants to conquer the Western world.Tremain was critically injured during subsequent scientific experiments before being rescued by the mutant soldier Cable and his mercenary ally G.W. Bridge. Cable infused Tremain with his blood-despite the risk of infecting Tremain with the techno-organic virus within his own system-and kept Tremain's heart pumping with his telekinetic powers so that Tremain would live long enough for Cable to take him across China to a hospital. Cable later took Tremain back to America to meet with Professor Charles Xavier, mutant telepath and founder of the X-Men, who showed Tremain the possibility that man and mutant could coexist.
After Xavier spawn the powerful psionic creature Onslaught, Tremain was lured into his service. Onslaught used the techno-organic virus within Tremain to transform him into the cybernetic powerhouse Post. Acting as Onslaught's "Herald," Post was assigned to test the X-Men's limitations in order to determine their whether they were worthy of Onslaught's coming. Onslaught had the Aboriginal mutant Gateway teleport Cyclops, Storm, Iceman and Wolverine to a remote location where Post, attacked them. He held his own against the foursome until they used team work to defeat him. Post was subsequently instructed to eliminate Cable, whom Onslaught believed posed a treat to his plans. After blowing the freighter base of Cable's mentor Blaquesmith, Post beat Cable nearly to death.Subsequently, Post teamed up with Onslaught's other thralls to oppose the government sponsored X-Factor team's efforts to prevent Onslaught from gaining control a fleet of Sentinels. Post then joined his fellow thrall Holocaust in fighting the Avengers, but was defeated after Captain America tricked Holocaust into blasting Post.
Post later resurfaced as a member of the Blob's new Brotherhood of Mutants, who sought to safeguard Xavier from the threat of the nanite-infested rouge computer Cerebro. Alongside the X-Men, Post and the Brotherhood fought against Cerebro's Cerebrite Beta but were defeated. After Xavier defeated Cerebro, he returned to the X-Men. Post and the Brotherhood were recruited by the mutant terrorist Mystique, who sought to capture the head of the robot Machine Man (X-51). Fashioning a new body for itself, X-51 clashed with the Brotherhood and overrode Post's control of his weapons pods, seriously injuring him. After the battle Post escaped into the labyrinth of tunnels underneath New York City, former home of the mutant Morlocks. From there he contacted Cable and confronted him over their shared past. After a brief scuffle, Cable offered Post a second chance, and his sincere generosity convinced Post to strive for better future.