The Horsemen of Apocalypse are mutants who have given their body and soul to the will of Apocalypse and proudly serve as his advance guard and shock troops. The initial team consisted of Candra, Gideon, War, Death and Sabretooth. Their first mission was to enter Cape Citadel and gain entry into locating all of the U.S. missiles around the world and launch them. When Sabretooth learned what they were planning on doing he began to have second thoughts about completing the mission. When Apocalypse learned about this, he ordered his Horsemen to kill Sabretooth but the arrival of the X-Men prevented this from occurring. While Gideon continued with launching the missiles, the Horsemen of Apocalypse and the X-Men fought each other. As this was going on, Nemesis, an agent of Apocalypse, sought to impress his master by attacking the X-Men base. His attack was held off by Rogue and Magneto's daughter, the Scarlet Witch. During the assault, Nemesis successfully killed the Scarlet Witch before departing. Magneto entered Cape Citadel and drew power from Earth’s magnetic field, amplifying Gideon's own powers and killing him. With the launch sequence terminated, Apocalypse ordered his Horsemen to return with him, except for Sabretooth whom he no longer considered worthy to his cause. Sabretooth would later reform and join up with the X-Men.
One Horseman of Apocalypse, the second Death, sought to usurp power for himself. However he was stopped by the X-Men and Cyclops, who briefly teamed-up with the X-Men to take down Death. Cyclops released Sunfire from Death's prison and Sunfire exacted his revenge by killing Death. Nemesis, now calling himself Holocaust, later slew Candra for working with the Assassin’s Guild and became a Horseman. Another mutant, Mikhail Rasputin, the brother of Colossus, opposed Apocalypse’s rule and killed the Horseman War. However, Apocalypse was so impressed with Mikhail's conquest he made him one of his Horsemen. Abyss broke out of Sinister's lab and killed a Horseman named Bastion. However, Apocalypse chose to make him a Horseman himself instead of killing him. Thus, a new team consisting of Abyss, Sinister, Mikhail and Holocaust arose and each had the responsibility of presiding over a quarter of Apocalypse's domain.
Sinister realized that his master was becoming fanatical and that their vision of the future didn’t coincide with one another. He secretly created a mutant that would have enough power to end Apocalypse's rule. This mutant would become known as X-Man and Sinister hid him amongst a traveling troupe of mutants. Sinister's betrayal eventually came out in the open after it was revealed that he gave information concerning Apocalypse's future plans to Weapon X and Jean Grey. Sinister later blew up the statue of Apocalypse in New York before going undercover to find X-Man. Sinister, donning a disguise and calling himself Essex, joined up with X-Man and his friends, including his mentor Forge. However Forge did not trust Essex and Brute eventually recognized him from the time he spent in Sinister's breeding pens. Sinister killed both Brute and Forge and X-Man, overcome with fury, unleashed his powers on Sinister, apparently killing him.
Apocalypse gave Abyss the mission of stopping the Sentinels and the X-Men from helping the humans evacuate from Maine. He kidnapped a young boy as an attempt to lure the X-Men to him. Unfortunately he grew distracted from his mission by trying to capture Quicksilver as a means to impress his master. Quicksilver, with the aid of Storm, defeated Abyss and rescued the boy. However the X-Men once again encountered Abyss while trying to rescue Bishop from Apocalypse's forces. Banshee used his sonic scream to rip Abyss apart apparently killing them both.
Mikhail Rasputin, dubbed “the Forgotten Horseman” by some, approached the Human High Council with a message of peace. Unfortunately Mikhail had no intention of fulfilling this message and his plans were opposed by agents of the High Council. During the battle, Donald Blake pushed Mikhail out of the Big Ben, killing them both. During the final battle between the X-Men and Apocalypse, Holocaust was stabbed in the chest with a shard of the M'Krann Crystal and both were transported to the Marvel Universe. With Apocalypse's defeat assured, there has been no need for new Horsemen.