The Four Horsemen of the Apocalypse are arguably one of the most famous Biblical figures other than Satan himself, though they are not necessarily entirely fueled by malice, acting as divine harbingers of the End Times.
Description
These four powerful beings embody four apocalyptic forces that are said to be granted authority over the world until the Day of Judgement when God himself shall manifest and create a new world free from all sin. The Christian apocalyptic vision is that the four horsemen are to set a divine apocalypse upon the world as harbingers of the Last Judgement. They are popular figures in doomsday writings and continue to fascinate many, though they are seen more as symbolic figures in modern belief than literal beings.
Revelation tells of a book/scroll in God's right hand that is sealed with seven seals. The Lamb of God/Lion of Judah opens the first four of the seven seals, which summons four beings that ride out on white, red, black, and pale horses. To Zechariah, they are described as "the ones whom the Lord has sent to patrol the earth" causing it to rest quietly. Ezekiel lists them as "sword, famine, wild beasts, and plague."
In John's Revelations, the first horseman is on a white horse, carrying a bow, and given a crown, riding forward as a figure of Conquest, perhaps invoking Pestilence, Christ, or the Antichrist. The second carries a sword and rides a red horse and is the creator of War. The third is a food merchant riding upon a black horse, symbolizing Famine. The fourth and final horse is pale green, and upon it rides Death accompanied by Hades. "They were given authority over a quarter of the earth, to kill with sword, famine, and plague, and by means of the beasts of the earth."
Overview
The Horsemen were born from Sin, the daughter of Satan, and they were born in consecutive accordance to the forces that plagued existence and humanity for untold millennia. The Horsemen are believed to either serve God or Satan depending on the version. However, the Horsemen themselves confirm that they answer to no higher authority implying that not even Heaven holds sway over them nor do the legions of Hell. All they are committed to is the task that they have been preparing for since the time of their conception.
The Four Horsemen are pivotal in their roles regarding the Apocalypse. When Lucifer rises from his tomb, he will summon the Horsemen through the release of the first four seals across four locations which are plagued by what they embody. After which, their main task upon their release is to travel towards where the four Towers of Babel are hidden in the Four Corners of the World, all while inciting chaos in their wake and absorbing that chaos into themselves to provide them the power to summon the Towers of Babel as well as condition the Earth for the resurrection of The Beast. The towers themselves could only rise with a sufficient enough supply of sin and ruin.
The Four Horsemen will travel across the globe as they leave a trail of destruction and despair in their wake. The Horsemen have a very slanted view of humanity, and some see themselves as just bringing out the evil that is already in humans. Both War and Famine, for example, have said humans "only need a little push" in order to do horrible things, and both have shown a level of disgust and contempt toward how easily corruptible humans are, and what they can do.
Powers and Abilities
The Four Horsemen are some of the most powerful agents of the Apocalypse with their sheer presence alone being enough to turn society into ruin and death. According to Immanuel, facing the horsemen together would be suicidal even with the combined might of the main organizations. Moreover, even facing the horsemen individually their chances of beating them are quite slim.
The power behind the individual Four Horsemen was evident when Miguel's wolf pack from the Order of the Silver Cross greatly struggled against Famine, Conquest casually toying with Hellboy and Nero even when the latter was in Devil Trigger, and even Alucard himself struggled considerably against War to the point where his regeneration could not keep up with War's onslaught of attacks. Lastly, the combined might of the Sun Moth, Spawn, along with Klaus and Steven Starphase from Libra were not enough to have Death exert effort.
The Horseman are ancient primordial concepts which have tormented the Earth since time immemorial personified. The forces which they embody affects all around them as War's presence caused the people of Oklahoma to become barbaric and battle-crazed lunatics. The more humans give into their instincts which are nurtured and instigated by the Horsemen, the more the Horsemen themselves become stronger. The air that reeks of chaos, ruin, and death that happens around them because of their actions is absorbed by them, which in turn empowers and provides them with more than enough power to raise the Four Towers of Babel.
The Horsemen are for all intents and purpose unstoppable, however, even though they can be defeated by some other mighty force, they merely rise up once more to finish their task. To truly defeat these beings is to reassemble the four seals that summoned the Four Horsemen in the first place.