"The obvious mutant is nothing but a target. The mutant whose changes are subtle represents the greatest risk of contagion."

Apothecary Tarben Hovak, Howling Griffons

Mahir is a Death World of the Jericho Reach that, historically, has been of only limited interest to the Imperium. It has few resources of value and is scarcely habitable by Humanity.

Over the last two Terran years, that has changed substantially. Tyranid forces from Hive Fleet Dagon have begun the process of invading and the T'au responded to the assault by sending their own forces.

Trapped between these two xenos forces are the few Human descendants of ancient colonial efforts.

The interactions of these three groups have compelled the Deathwatch to gather additional information. Firsthand knowledge of the xenos conflict is invaluable to the Inquisition.

It might even lead to a way to assure the destruction of both alien forces as they war with one another, leaving them vulnerable to later Imperial efforts.

A decision needs to be made soon about passing this information on to the Achilus Crusade, as there could be significant ramifications.



During the height of the ancient Jericho Sector, there were numerous organisations interested in exploring new worlds and establishing colonies. Some did so out of simple greed -- a successful colony could provide substantial profits to a merchant house or a noble family.

Not every world can easily be made profitable, however. In fact, there are many worlds within the Jericho Reach that are habitable but that lack any resource that could be used to recoup the costs of colonisation. Mahir represents one such world.

The combination of limited resources and treacherous wildlife makes Mahir inimical towards Humanity. In spite of this, there were at least four known colonisation attempts sponsored by different groups active during the Jericho Sector's Golden Age.

Some of these colonists were staunch survivalists, who could not resist the challenge that the world presented. Others were motivated by the power and glory that came with an opportunity to expand the Imperium's reach to an unoccupied world.

At least one is believed to have been an effort initiated by Renegades who attempted to establish a foothold outside of the Imperium's direct control.

To say that all of these attempts ended in miserable failure would be an exaggeration. Descendants of at least one of these groups of colonists still dwell upon the planet, though it is unclear if they are descendants of survivors from one or several of those ancient efforts. However, this does not mean that any of the colonies were successful.

Few records survive to recount these ancient efforts. Those that remain recount substantial expenses incurred by the colonisation attempts, but there are no existing records of any recovered expenses.

Imperial records indicate a horrific death rate during each colony's existence. The cost to transport and provide for these citizens, all so that they could fail to found a colony, is staggering.


Without regular support from the sector, none of Mahir's colonies were self-sustaining as implemented. There were too few agricultural resources to begin to provide for all the Humans who had been sent to Mahir.

Few who lived on the world had the necessary training to either maintain the world's equipment or to fend for themselves in the face of the Death World's countless threats.

A few short solar months after the last supply transport departed from the world, the world's Human population nearly died out. Those who survived fled from the established habitats. Within them, the inhabitants soon turned against one another in desperate battles for food, energy, and the other necessities of Imperial life.

With time, even the victors of those battles died out, as their last supplies ran low and technology continued to fail. Soon, the world's native wildlife intruded upon the ancient Imperial structures and destroyed virtually all trace of their ever having existed.

Among the distant outposts were many of the colony's most capable frontiersmen. The hunters and warriors who had adapted to the intricacies of Mahir's ecosystems were the ones most willing to learn to rely upon it.

Lacking standard equipment and supplies, these hardy individuals devised ways to create basic weapons and eke out a subsistence existence. At least some of these survivors reverted to arboreal lifestyles, creating communities within the highest branches of the world's massive trees.

Clearly, many of these small communities perished. While none have thrived, a scarce few survived through the millennia without any external support. During this time, their cultural identity diverged substantially from the Imperial norm. However, their legends remained rooted in the teachings of the Imperial Cult.

They continued to venerate the Emperor as the "Sky-Father." This belief may have saved these primitives from the influence of Chaos that devastated so many other worlds of the Jericho Reach.

End of the 41st Millennium

In 814.M41, T'au forces sent an expedition to Mahir. The xenos incursion was little more than an exploratory mission. As past Imperial efforts have shown, all astronomical data suggest that the world might be an ideal candidate for colonisation.

T'au environmental tolerances are sufficiently similar to Humanity's that worlds well-suited for one species are often adequate for the other. All signs indicate that T'au forces reached the system with the intention of discovering whether it could be easily colonised and to determine what assets its world might offer.

As there were no Imperial assets within the system at this time, Deathwatch forces did not become aware of the incursion until 815.M41.

They learned of the activity when a team in service of Inquisitor Ezu Ghraile was sent to the world to study its native inhabitants. Ostensibly, the agents were to examine samples of the world's native life forms as well as genetic material from the primitive Humans.

These were to be examined for any signs of contagion -- possibly including any indications of Tyranid influence. Unfortunately, the agents discovered information that was far more disturbing. Upon their arrival, they soon detected the presence of voidcraft-affiliated with the T'au Empire, as well as a small fleet of Tyranid biocraft in system.

The single Inquisition voidcraft was forced to rely upon stealth to avoid a direct confrontation with either of the two much larger xenos forces.

Through a series of slow and steady manoeuvres over the course of seven solar months, the vessel managed to obtain a supply of raw data regarding the alien activities on Mahir. It then fled back to Watch Fortress Erioch, so that the information could be presented to the Inquisitor and to the Deathwatch.

The news of a direct conflict between these two xenos species has led to substantial disagreements among the Inquisitors present at the watch fortress. As of yet, there is no consensus regarding the most appropriate response.


The world's few surviving Humans are descended from those who fled the Imperial colonies to establish their own outposts as the world's civilisations collapsed.

These hardy folk know little of technology and only have the most rudimentary of language skills. Much of their technology consists of weapons and tools crafted from the shells of the world's countless insect analogues.

Extended exposure to Mahir's harsh environs and separation from advanced Imperial medical technology has clearly had ramifications as well. Ultimately, these primitives are of Human stock, but they have suffered enough minor mutations that the Inquisition might no longer deem them acceptable.

Only a rigorous analysis of genetic samples could effectively resolve this concern. If such a study was completed and no anomalies were found, Imperial forces might be able to reintegrate these Humans with the Imperium.

Their beliefs are clearly derived from Imperial teachings, such that missionaries could quickly purge the heretical elements and accept their devotion.

The T'au forces that initially travelled to Mahir did so with the intention of examining the planet. This contingent of xenos had only a minimal military presence, and instead was comprised primarily of members of the Earth Caste. It is unclear how long they were involved in their research prior to the arrival of Tyranid forces within the Mahir System.

However, the Velk'Han Sept committed a substantial amount of resources to the world once they became aware of the Tyranid incursion. While the T'au have only a limited degree of historical experience fighting Tyranids, their presence on Mahir could swiftly change this.

By all indications, the T'au are engaged in a deliberate effort to completely repel the Tyranid attack without actually destroying the planet's biosphere. Currently, they lack the required forces within the system to succeed at this task.

They would need to send additional troops to Mahir to aid in these battles, but doing so could be extremely advantageous for the Imperial forces within the Canis Salient.

The T'au could be deliberately delaying from committing additional troops until they see how Lord Commander Sebiascor Ebongrave deploys his forces within that region of space.

The Tyranid incursion on Mahir is still at a fairly early stage, but it is clear that the world's ecosystem is incapable of directly contesting the xenos threat. Nearly twenty percent of the planet's surface has already been devoured by the swarm.

Only those places that the T'au are actively defending are capable of standing up against the incursion. Were it not for these xenos, it is likely that Mahir would already have fallen to the Tyranids.

Indeed, the Tyranids have already begun to adapt to Mahir's environment. The Mahir Leaper is a notable gaunt-variant first observed on this world. The creature is smaller than most known gaunt specimens, but is also faster and more agile.

Reports suggest that this biomorph is an adaptation enabling it to more effectively wage war among the branches of the planet's massive trees.

In these locations, the reduced size and added agility enable it to more effectively hunt in the arboreal habitats. This is likely to target some of the native life forms, rather than the limited Human population -- those Humans are simply too poorly armed to offer any significant threat against the Tyranids.

Geography, Flora and Fauna

Mahir positively teems with life. Its dense temperate forests cover virtually the entirety of the world's land. Only its rivers and oceans break up the seemingly endless foliage.

In fact, the world is so burgeoning with life that much of it lives in defiance of gravity, as many of the world's enormous trees extend hundreds of metres above the ground and house their own ecosystems.

However, the intrusions of the Tyranid swarm could render all of this life little more than biomass to feed the ravenous xenos. All of Mahir's unique characteristics still exist, but if the Tyranids triumph, the world would be left as little more than a barren wasteland.

Mahir's climate is remarkably consistent. It is unclear if this is a consequence of atmospheric anomalies, variance in its orbit and rotation, or an unknown characteristic, but there is very little temperature variation across most of the world's surface.

From an area very near its polar caps and extending across the equator, the world's temperature consistently holds steady in a range between 20 and 30 degrees centigrade.

The world's seasonal changes are subtle and primarily deal with the amount of precipitation during different local months, but even this variation is not extreme. Such consistency has drawn the attention of members of the Adeptus Mechanicus as a planetary anomaly.

There has been some speculation that this is an indication that the planet had been seriously manipulated at some point in its ancient history.

Some argue that the world's greatest failing is further evidence of such manipulation.

Simply put, Mahir has an extremely limited supply of workable metals. While some exist at low levels within its native organisms, there are very few metallic ore deposits within its crust.

The Imperium's technology base lacks any efficient way to extract enough materials from Mahir to effectively construct a hive city. This could also have played a key factor in the failures of past Imperial colonial attempts.

This limited selection of metals have also played a factor in the development of the world's biosphere. To state that all of its organisms are aggressive understates the severity of Mahir's indigenous species.

All of the world's animals and many of its plants are seemingly engaged in an unending drive to consume any source of metals that they can find. In their natural state, this primarily consists of other organisms, which carnivorous flora and fauna target for consumption. However, any visitor to the world is targeted, along with their metallic equipment.

Mahir's organisms are extremely persistent in their attempts to use their acidic saliva to break down metals so that they can absorb them.

Excepting the massive tree analogues which make up the majority of the forest, much of the world's flora demonstrate some degree of motility. This is believed to be an adaptation to assist them in their endless quest to identify further sources of metals. While these sources include ores within the planet's soil, it also includes any slow-moving animals.

All of Mahir's animals are multi-limbed invertebrates analogous to Terran arthopods and insects. These organisms vary in size from near microscopic up to nearly 30 centimetres in length. All known specimens exhibit thick, organic carapaces.

Many of these are extremely resistant to damage, including acidic attacks. This is most likely an adaptation to the world's aggressive plant-life, but also to the efforts of the world's other animals. From an ecological niche standpoint, these animals occupy a diverse range of habitats.

They are present throughout Mahir's various biomes and demonstrate a broad range of different adaptations. Most of these creatures are particularly active at night, because after the sun sets, the world's plants are typically much less motile and vulnerable to predation.


  • Deathwatch: The Outer Reach (RPG), pp. 82-84
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