The four horseman are Apocalypse's personal warriors and always play a key role in his plans for mutant conquest and domination. The enhancements made to horseman are often a combination of both biological or genetic manipulation and the employment of the celestial technology that Apocalypse uses.
The use of the four horseman specifically is largely symbolic, and their powers are often either directly or closely related to their namesake. When mutants (or in some cases humans) that are to become horseman are chosen that do not have desired powers, Apocalypse will augment their powers to more closely resemble their role or give them new powers entirely. Regardless, the powers and abilities of a horseman are generally augmented or enhanced to serve Apocalypse's purposes.
Apocalypse is also known to brainwash reluctant horseman to become more obedient soldiers. Several horseman have been able to overcome Apocalypse's programming by sheer force of will. While brainwashing can be overcome, the transformation process can still be psychologically damaging and can haunt former horseman long after leaving Apocalypse's servitude.
Lastly, as a side effect of the transformation process a horseman's appearance will often change. This can be because of more obvious changes such as Archangel's metal wings, skin and hair color changes such as in Gambit and Angel as death, or other physical changes such as the enlarged stature and mass of Gazer as war.
The Horsemen of Apocalypse were originally created by Louise Jones Simonson and Walter Simonson.
The First Horsemen
The first four Horsemen Apocalypse ever recruited were Plague who he recruited during the mutant massacre as Pestilence. The second was Abraham Kieros who was War. Autumn Rolfson was his 3rd recruit he became Famine and the last one of the first Horsemen was the de-winged Angel who became Death (the Achangel) who was given razor sharp Metal wings and Blue skin.
The 4 horsemen fought each other to see who would be their leader Death(Archangel) won. Soon afterwards they fought X-Factor which they nearly lost till Death appeared. Caliban came to Apocalypse to get more power to avenge the Morlocks, who were killed during the Mutant Massacre. Since Pestilence (Plague) was killed and Archangel came back to his sense after he believed he killed Iceman, Caliban became the new Pestilence.
Caliban captured Jean Grey and Cyclops under orders of Mr. Sinister. The X-Men came to the rescue and defeated Famine, Caliban, and Abraham Kieros (War). The X-Men were then later defeated by Apocalypse.
In a battle with the X-men, the Hulk was defeated, found by Apocalypse, and made into the new War. To test his strength he was pitted against the Juggernaut, whom he pushed back. He also defeated Absorbing Man. He then came to his sense after injuring Rick Jones.
Apocalypse: The Twelve
Before and during the Apocalypse: The Twelve story arc Wolverine became the new Death and Caliban became Pestilence. The new War was Deathbird, and Ahab became Famine.
Feeling that his leadership was more in need after the M-Day than ever before, Apocalypse emerged once again to lead the remaining mutant population against the human majority. In a move which could have been motivated by Apocalypse's narcissistic use of symbolism, the majority of the mutants that he selected for his next team of Horseman were de-powered on M-Day. The first Horseman Apocalypse recruited for his new team was Gazer, a mutant who was a part of a NASA research program, whose loss of power on M-Day left him dying of radiation poisoning. Gazer was pitted against a human archaeologist in a fight to the death to determine which would earn the first position of War. Unbeknownst to Apocalypse, Ozymandias the scribe of Apocalypse allowed Gazer to survive so that Gazer would owe him a life debt he planned to collect when he decided to turn on Apocalypse.
The next Horseman selected was the mutant Sunfire, who had lost his legs in a fight with Lady Deathstrike. Sunfire had allowed Rogue to take the remainder of his powers in order to finish the fight and defeat Lady Deathstrike. Powerless and crippled, Sunfire was approached by Apocalypse who offered him his legs, power, and dignity in exchange for servitude as Famine. Sunfire was brought to Apocalypse's temple, where he tried to help Gazer escape. When Sunfire was finally able to get to Gazer it was far too late, as Gazer had been transformed into War in both body and mind.
Polaris had lost her powers on M-Day, and had ventured out into the world in an attempt to discover how to become whole once more. The alien Doop led Lorina to Apocalypse's temple where she would be given back her magnetic abilities, as well as the ability to carry and transmit some of the most lethal diseases known to man, as the horseman Pestilence.
Finally, overcome by feelings of loss and self-loathing, Gambit sought out Apocalypse to volunteer himself as one of the Horsemen. He explained to Apocalypse that he almost believes he is on the mutants' side, feeling that M-Day has brought out the best of Apocalypse. He also warned Apocalypse of betrayal, stating that he would be there right at his side should the "old" Apocalypse show his face, waiting and watching for the X-Men. Gambit was given the ability to remotely transmute gases into poison. His skin was also turned black to reflect his new role as Death.
When Ozymandias called upon Gazer to fulfill his portion of their arrangement, Gazer refused to turn on his master. Upon refusing, Ozymandias ran Gazer through with his sword right in front of Apocalypse. Gazer had also lead the X-Men into Apocalypse's temple, where they found Polaris. They took her back to the X-Mansion to receive heal from her transformation. Sunfire and Gambit were seemingly able to break free from Apocalypse's control and fled together, knowing that only each other would understand what they went through.
Gazer is now dead. Lorna is back with the X-Men, and has been healed from her exposure to all of the diseases she encountered as Pestilence. She is adjusting to the magnetic powers that Apocalypse restored in her. Her powers are currently unwieldy and difficult to control, and seem to be technologically based now, rather than biologically. Gambit and Sunfire, looking for a new direction in their shattered lives, were approached by Mister Sinister with the invitation to join his new incarnation of the Marauders. They accepted. Apocalypse was killed but has apparently resurrected himself by ingraining his genes in an innocent little boy. Clan Akkaba is presently trying to indoctrinate him into being a carbon-copy of Apocalypse.
A whole new cadre of unbelievably powerful Horsemen calling themselves, The Final Horsemen . They were all separately assembled by Apocalypse and Ozymandias. They come into confrontation with the new X-Force and easily defeated and separated them.
The Final Horsemen are Apocalypse's last resort team of horsemen, "To be awoken only when all other approaches have failed." They consist of Decimus Furius as War, Jeb Lee as Famine, Ichisumi as Pestilence, and Sanjar Javeed as Death.
Decimus Furius was the son of a philosopher that was originally alive in Rome during the 200's. When his father committed suicide and his mother died shortly after, he was left homeless, without any money. While slowly starving to death in a alley, he transformed into his mutant self. When he was seen the human civilians attempted to kill him. He slaughtered dozens before being brought down. Eventually, after being imprisoned for years, he was offered freedom, providing he was able to defeat all others in the arena. With his axe, he slaughtered all who opposed him. He was then worshiped as the Dark God Minotaur. He was found by Apocalypse and Ozymandias while they were searching for there Final Horsemen, and he was appointed as War.
Jeb Lee was a Confederate spy that fought during the civil war. He marched behind enemy lines disguised as a Union drummer, gathering information. After the war he returned home, mistakenly wearing his Union uniform. The confederate's believed him to be a traitor and burned his family alive in front of him. This stimulated his latent mutant powers. From then on Jeb marched from battle to battle unleashing his power's on all he met.
Ichisumi first lived In Kumamoto, Japan in the year 1893 AD. As a geisha, she was jealous of all the more beautiful and intelligent women around her; as she suffered from a severe inferiority complex. Her father was a samurai who would get mad whenever she would fail. Stemming from her repressed rage and the disapproval of her father, she savagely ravaged the other geishas after releasing a swarm or "yume" beetles from her mouth. This is when Ichisumi's powers first manifested leading to her "collection" by Apocalypse, as his Pestilence.
Sanjar Javeed was the illegitimate son of King Shapur II and one of his servants. The King could not let out that he had this son, therefore Sanjar turned to thievery to get the attention of his father. However, this was when Sanjar's powers developed. He began to poison the entire kingdom by spreading diseases through the stolen treasures. On his deathbed King Shapur named his son the "The Seraph of Death". Soon Sanjar was collected by Apocalypse as his horsemen, Death.
As the X-Force team return from the Age of Apocalypse world, they find Archangel has arisen to his full potential as the new Apocalypse. With this, the Final Horsemen return as well, however, they now have a new addition to the team. Now, a young boy named Genocide has taken up a major part of the team. Using his extremely strong powers, Genocide manages to destroy an entire town populated by over 3,000 civilians. Genocide is the son of the original Plague. He was hidden from Apocalypse because his mother thought he may be killed by him if he was seen as a rival. As of late, he has been Archangels powerhouse, becoming a major threat to the entire X-Force Team. This isn't just theoretical either. Genocide blasted Wolverine, removing all the flesh down to his bones.
The rest of the Final Horsemen have been in action as well. Pestilence had been assigned to Psylocke's guard, but was taken out by her after being stabbed through the mouth with her own parasol. Famine, of Jeb Lee was captured by X-Force. Deathlok tortured him for many hours while his host took control, revealing the location of Archangel to the team. Finally, Death was killed by the X-Force team.
At the moment, the Final Horsemen are incapacitated, however, with Genocide still at Archangel-Apocalypses side, they are near unbeatable.
In the Age of Apocalypse reality the horsemen were: Sinister, Holocaust, Mikhail Rasputin and Abyss.
In this reality the horsemen were: Archangel (Death), Spider-Man (Pestilence), Cable (War) and Blob (Famine).
In this reality, Mr. Sinister was the only horseman to be mentioned.
Angel is the horsemen of death. He has bat-like wing, he could breathe fire and change his name to "the Fallen". He aligned himself with Havok and his team "the Six", but returned to Apocalypse's side to battle an evil Professor X.
On one of the Exiles's missions, they encountered a version of Thunderbird as the horseman of War. he managed to overpower Apocalypse's influence in him and came back to his old allied, the X-Men.
In the House of M, only Iceman was mentioned as a horseman but it is unknown what title he held. He was sent by Apocalypse to attack the country of Wakanda to kill Black Panther.
In the Marvel Mangaverse, the horsemen is composed of Archangel, Juggernaut, Mister Sinister and Emma Frost.
X-Men: The Animated Series
The Horsemen appeared in Come the Apocalypse (Episode 10) of the animated series, this is another time the cartoon followed comics and had the original four horsemen as the horseman.
In the animated series, X-Men:Evolution, the four horsemen of Apocalypse are Professor Charles Xavier, Storm, Magneto and Mystique.