Summary
In the grimdark future of theWarhammer 40Kuniverse, there is only war. Entire worlds and sectors have been engulfed in flames or have become new battlegrounds. Progress and peace are relics of the past, and the line between good and evil is lost,leaving numerous groups to their devices in a galaxy-wide war seemingly without end. Such conditions have birthed many powerful factions with skills and abilities far beyond comprehension. However, which of these factions is the strongest?
Warhammer 40Kfans participate in great debates on forums and discussion boards everywhere, disputing which factions are the most powerful, with disagreements abounding. Many factors and events go into deciding which side of this galaxy-wide war is the best, and the ever-growing universe ofWarhammer 40Kalways seems to rock the power balance. This trend of shifting scales has caused some fans to separate the factions into two categories, those that appear to be growing or evolving and those that are shrinking or regressing —making allocating each faction’s power somewhat easier. Yet, one thing is sure: each side has the potential to overcome the other, and no faction shows signs of backing down.
Updated June 07, 2025, by Andy Chapman: Warhammer 40k has continued to grow into a popular mainstream setting. With the announcement that the Amazon Prime film and TV deal has been finalized, interest in the IP will only increase. The setting has also been featured in an episode of the animated series Secret Level. The episode titled They Shall Know No Fear is the best and most brutal depiction of Space Marines seen on screen yet. In the hobby itself, The Emperor’s Children faction has finally been revealed to eager fans looking to start a new Chaos army. This article has been updated with four additional entries to further expand on the many factions featured in Warhammer 40k.
25Chaos Knights
Ancient War Machine Corrupted by Chaos
The emergence of Chaos Knights can be, once again, traced back to the Horus Heresy, the galactic-wide civil war that split humanity in two. However, the Knightly houses that own these gargantuan war machines can trace their lineage to humanity’s great expansion into the Milky Way during the Dark Age of Technology. When the Age of Strife hit, and Humanity was cut off from one another, planets that enjoyed the protection of Knights would enjoy a much higher level of peace than many others in the galaxy. These houses wouldn’t eventually be brought into the Imperium during the Great Crusade.
Fast-forward to the Horus Heresy, and this peace was finally broken when many of these Knightly houses and Mechanicus forge worlds would align themselves with the traitors. As the houses turned renegade, many would fall to Chaos, and with them, their colossal Knights changed. Chaos Knights are walking death machines that can level entire cities. While they are few, a single Knight can change the course of a battle, spreading destruction wherever they go. Chaos Knights are a powerful tool for the forces of Chaos, making them an influential resource during planetary campaigns.
24Imperial Knights
Ancient War Machines Towering Over Battlefields
These ancient war machines tower above battlefields, destroying humanity’s enemies with devastating power and weaponry. While they are dedicated servants of the God-Emperor, theImperial Knights’true legacy stretches back before the imperium and into humanity’s golden age. Each of these colossal robotic machines is piloted by a single human who comes from a different aristocratic family, who can often trace their lineage back thousands of years.
When humanity first stretched out into the galaxy and began to colonize millions of worlds, many found their new homes extremely hostile. To protect themselves, they used AI-based technology known as STCs, or Standard Template Constructs, to develop enormous machines capable of protecting the human settlers. Over time, these planets would come to revere these machines, as well as the pilots who controlled them. When the Emperor of Mankind reunited humanity and started his Great Crusade, many of these noble families were brought into the imperial fold, lending their strength against humanity’s enemies. In the modern setting, these ancient machines are maintained by the Adeptus Mechanicus but are still piloted by the same noble families who march to war representing both the honor of their family and the might of the imperium.
23Dark Mechanicum
Masters of Dark Technologies
After Warmaster Horus declared open rebellion against his father, the Emperor, the entire Imperium was plunged into civil war. This stretched across the galaxy as sides were chosen. Among the forges of Mars, the tech-priests of the Cult Mechanicus were split in two when Fabricator General Kelbor-Hal was persuaded to join the heresy. Brought over by the promise of unlimited access to forbidden secrets, including outlawed AI technology, this new sect of tech-priests would come to be known as the Dark Mechanicum.
Much like their loyalist counterparts, the Dark Mechanicum seek deeper knowledge and connection with their deity, the Omnissiah. However, unlike the loyalists, they believe their god is embodied through Chaos Undivided rather than the Emperor of Mankind. The Dark Mechanicum works much like the Adeptus Mechanicus does for the Imperium by maintaining the many war machines used in battle. However, the Renegade Tech-Priests are not censured for strange, warp technologies or artificial intelligences like the Adeptus Mechanicus. While the Dark Mechanicum acts more as a support faction for the armies of Chaos, their expertise and continued research into forbidden knowledge make them an influential and dangerous faction in the40ksetting.
22Genestealer Cults
An Insidious Virus Spreading Through Populations
One of the most insidious dangers that threatens the safety of Imperium is from within.Genestealer Cultshave become a common occurrence across the vast reaches of the galaxy. Worlds are suddenly going dark as cells become active and destroy populations. The Genestealer Cults are secretive societies of humans that have come to worship a xenos god. Controlled by a powerful breed of Genestealer known as a Patriarch, which can lie dormant for generations, the Cults slowly infect a population. It can take generations for a cult to be ready, with the cell growing and spreading year after year into every echelon of a planet’s society. Some members within the cults will eventually deform, becoming more like the xenos they worship, with new arms growing, and their heads becoming bulbous and alien. Although most appear like any other citizen.
Once the Genestealer Cult has grown to a large enough size, they will attack at once. When there are cultists in every part of society, a planet can fall overnight. Once they have successfully taken over a planet, the psykers within the Cult will send out a call to their xenos god. The tragedy of the Genestealer Cults is that the god they worship is the Tyranid Hivemind. The psychic call reaches out to a hive fleet, which descends onto the planet and proceeds to devour all organic life, human and cultist alike. Genestealer Cults have spread to every sector of the Imperium and are slowly weakening the foundations, ready for the great devourer to come.
21Imperial Agents
The Secretive Few, Fighting Humanity’s Enemies
From the deadly killers of the Officio Assassinorum to the feared agents of the Inquisition, to famed Rogue Traders, forging new paths through the galaxy: theImperial Agentsoften work from shadows but wield immense power. The Imperial agents are not one unified faction, but rather a collaboration between the many departments of the Imperium of Man. Imperial Assassins are some of the deadliest killers in the galaxy and can efficiently deal with any single threat, while the Rogue Traders carve new paths through the galaxy with unprecedented freedom.
Inquisitors are the front line of investigation, often working alone or with a small retinue. They seek to uncover treachery, heresy, or xenos plots against humanity. They answer to no one but the Emperor himself and can call down the vast strength of the Imperium if they see fit. These forces can include elements of the Astra Militarum, the planet’s local defense force, sisters of the Adepta Sororitas, and in extreme cases, the Adeptus Astartes Deathwatch chapter. This unique force is made up of the elite veterans from other Astartes chapters and serves the Ordo Xenos of the Inquisition. The Deathwatch is the last resort for Inquisitors, who only call upon them in their greatest need.
20Ynnari
The Last Hope of the Aeldari
One of the newest factions of the Aeldari race, the Ynnari are followers of the unborn Eldar god of the dead, Ynnead. Only partially awakened by the High Farseer Eldrad Ulthran, due to the intervention of the Deathwatch, Ynnead’s power would find a corsair and Commorragh gladiator named Yvraine as she lay dying on the ground. Known as The Daughter of Shades, Yvraine would become Ynnead’s prophet and found a new order named The Ynnari.
This new influential group, which includes Craftworld, Exodite, Drukhari, and Harlequin Eldar, seeks to awaken Ynnead fully. To do this, the Ynnari seek the legendary Crone Swords of the Aeldari Crone Goddess Morai-Heg. Once united, it is said, Ynnead will rise and destroy Slannesh once and for all, saving the souls of the Aeldari forever. With the power of Ynnead behind her, Yvraine is a powerful and influential figure among the Eldar. She helped to bring Roboute Guilliman back from his 10,000-year stasis, gaining further influence among humanity. While the Ynnari are a relatively small group, they are seen by many as the last hope of the race and are quickly growing in numbers, power and influence.
19Drukhari
Sadistic Seekers Of Pleasure And Pain
The Aeldari race once ruled the galaxy. Their vast empire rose to such technological advances that nothing was out of their grasp. Morality and ethics would be forgotten as the Aeldari continued down its dark road of depravity. As this continued, some would oppose the excesses of their race and travel to the galaxy’s far reaches in continent size Craftworlds. Others, who sought the darkest forms of entertainment would travel into the Webway, where every sadistic dream could be fulfilled.
When the Aeldari fell, with the cataclysmic birth of Slaanesh, those living in the Webway would escape death, but be forever cursed by the Chaos God. They became theDrukhari,and to save their souls from She who Thirsts, they must continue to inflict pain and torture on innocent beings. The Drukhari are not interested in expansion or domination, their lives revolve around pain. From the dark city of Commorragh, bands of Drukhari raid with lightning speed. After each raid, their unlucky victims are taken back into the webway, where they will experience years of pain and torture at the hands of Dark Eldar. While this faction is the most sadistic of all the races and enjoys powerful ancient Aeldari technology, they are much smaller than most. The Drukhari are content to hide away in the webway, safe from the glare of Slaanesh, to continue their their monstrous lives of torture.
18Adeptus Mechanicus
Worshipers Of Technology
TheAdeptus Mechanicus, or Cult Mechanicus, is a highly advanced civilization of humans on Mars that work symbiotically with the Imperium of Man yet are their own entity. Originally a colony from Terra, this faction evolved into a theological group that revered the Omnissiah — an obscure mechanical deity — with a penchant for maintaining and constructing machines. Although they worshipped a god, a practice deemed unacceptable by the Imperial Truth, the Emperor of Mankind accepted the Adeptus Mechanicus, granting them immunity so long as they equipped the Imperium of Man with the technology necessary for their galaxy-wide conquest. Few factions come close to the engineering prowess and intelligence of the Adeptus Mechanicus.
The Adeptus Mechanicus boasts access to one of the greatest armories in the galaxy, alongside powerful cybernetic enhancements that replace their weak flesh with technological wonders. So long as it is a tried and true invention that is not an innovation or abominable intelligence, it is at this faction’s disposal, granting them countless options and implements of war. With their superhuman smarts, the Adeptus Mechanicus can use these technologies to their fullest, making them dangerous opponents. But, while they are brilliant and with many devices of war, they are also independent, meaning their numbers and reach are comparatively small; moreover, they believe innovation to be heresy, preventing any advancement. Should the Adeptus Mechanicus bolster its numbers and innovate, little can challenge them, let alone stop them.
17Adepta Sororitas
Holy Warriors Of The Emperor
TheAdepta Sororitasis a religious order of warrior nuns within the state church known as the Ecclesiarchy, and are some of the most devout and fiercest followers of the God-Emperor of Mankind. Both feared and respected by millions of the Imperium’s subjects, the Sisters of Battle are a frontline defense againstheresy and rebellion. While the women of the Sororitas have no genetic augmentation and are all baseline humans, their immeasurable faith often manifests into minor miracles. Their prayers can heal wounds or miraculously avoid damage in battle altogether.
Unlike the standard Astra Militarum, the Adepta Sororitas goes to war in specialized power armor, giving them a higher level of protection over the common soldier. Their holy hymns are sung loudly as they storm their enemies, giving joy and hope to all who follow them. While they are some of humanity’s greatest warriors, they can also bring fear wherever they go, burning any they deem heretics. Over the millions of worlds that make up the Imperium of Man, it is often the Sororitas that are sent to put down the many uprisings that appear. The Sisters of Battle are some of the most elite warriors in the Imperium, and spread the faith of the Emperor wherever they go.
16Death Guard
Spreading Nurgle’s Gifts
The Death Guard, led by their Daemon Primarch Mortarion, are a scourge on the galaxy. One of the original 18 Space Marine legions, the Death Guard, would follow Horus into rebellion. Their true fall, however, would come later during the Horus Heresy, when First Captain Typhus would trick his legion and trap them in the warp. Here, Mortarion and his legion would succumb to the will of Nurgle, mutating into the horrific Plague Marines of Chaos.
Mortarion still leads his legion from his personal plague planet, now a powerful Daemon Primarch of Nurgle. While they often join forces with Warmaster, Abaddon the Despoiler, the Death Guard are a power unto themselves and seek only to spread Nurgle’s gifts of disease and rot around the galaxy. However, Mortarion has recently fallen from the favor of his patron god after failing to kill Roboute Guilliman. During the War of Ultramar, Mortarion would open a portal to the Garden of Nurgle, trying to corrupt his former brother. Before this could be accomplished, the Emperor possessed Guilliman, bringing him back to life, healing his wounds, and sending purging flames into the Realm of Chaos. This act would greatly weaken Nurgle.
