The Greyhell Front was a belt of worlds where the Astra Militarum and Imperial Navy were struggling to establish footholds closer to T'au space. Unlike earlier encounters with the Tau along the Canis Salient, the Greyhell front became a major warzone.
The Imperium's armies were opposed in this by many auxiliaries, but most of all by Fire Warrior cadres. Chief among the auxiliaries were legions of Kroot. The Kroot's capacity to rapidly evolve according to the genetic material they absorb has led to the development of many new strains of Kroot along the Greyhell Front.
Human collaborators also appeared in some numbers, leading to a paranoid atmosphere where any squadmate could potentially be an infiltrator sent by the other side. Lord Commander Ebongrave's purges on the Greyhell Front became the stuff of dark legend, and some joked that an Imperial Guardsman was almost as likely to be executed by their own side as to be killed by the xenos.
The Greyhell Front was regarded as a meat grinder by the troops serving there, but Lord Commander Ebongrave was adamant that only by forcing through the front and reaching Tau space could the crusade push on into a direct assault on the Velk'Han Sept. In spite of the thinly stretched nature of Imperial forces in the Canis Salient, Ebongrave refused any suggestion that Imperial forces should withdraw from the Greyhell Front. The Lord Commander was last seen boarding his Battleship, the Murder of Innocents, course set for the Greyhell front for "the final push."
The current status of the Greyhell isn't fully known. No Imperial ships have visited for decades, and the Tau are said to have pulled out of the area.
Notable worlds of the Greyhell Front:
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Baraban (Feral/Xenos World): Barabanis a is huge, verdant world under the control of the T'au Empire's Velk'Han Sept. Its ownership was contested by the Astra Militarum forces of the Achilus Crusade. The pretext for the invasion was "liberation of Baraban's native human population." It is not known if Baraban actually has any human native population, of it Ebongrave's staff made that up to "galvanize the hearts and minds of our noble warriors."
The war on Baraban was a conventional one, with battle lines of trenches and fortifications, attacks and counterattacks, as each side tried to push the other back. The planet's endless temperate forests were home not only to huge Vespid and Kroot armies, but to spectral presences that prey on the sanity of the Imperial Guardsmen fighting there. Apparently the "Ghosts of Baraban" caused similar problems for the Tau, with Vespids becoming homicidal and Kroots devolving into strains useless for battle.
Bekrin (Shrine/Quarnatined World): Bekrin was a Shrine World, the capital planet of the ancient Ecclesiarchy diocese covering much of what is now the Achilus Crusade's Canis Salient in the Jericho Reach. The Tau had little influence on Bekrin, and not for lack of trying. With the coming of the Crusade, Bekrin was incorporated into the Imperium once again, offering a forward base of operations for Ebongrave's warriors.
Unfortunately, a tendril of Hive Fleet Dagon, approached Bekrin. The planet's million-strong clergy evacuated the world to escape the approaching Tyranids, and though the Tyranids were deflected at Oertha, and never reached Bekrin, the planet's shrines and temples remained empty.
The Adeptus Ministorum petitioned Lord Commander Sebiascor Ebongrave to reclaim Bekrin many times. Ebongrave, for reasons unknown, has bluntly refused at every turn, and even proclaimed Bekrin a Quarantined World. No one knows why, though there is no shortage of speculation about what horrible sights might be found among Bekrin's fabled natural beauty and gilded temple-cities.
To some, Bekrin is an example of Ebongrave's paranoia, but others insist that there must be something terribly wrong with the planet. In any case, no official word on Bekrin has been forthcoming in more than forty standard years.
Dakinor (Dead World): Dakinor is a gas giant within tin the Canis Salient. It is surrounded by an orbiting shell of mineral-rich planetoids caught in its vast gravity. Classified as a Dead World by the Imperium, the planet itself is uninhabitable like all gas giants, but its asteroids are being fought over by the Astra Militarum and a host of fanatics following a death cult of the Imperial Creed calling itself the "Gilded Torment."
The Torment has absorbed almost the whole population, and has daughter cults on many worlds of the Greyhell Front's warzone, which task their followers with joining the struggle on Dakinor. The Gilded Torment's goal appears to be to cause and suffer violent death in the name of the God-Emperor, who is worshipped in such a debased and vile form that all followers of the Torment have been declared Excommunicate.
Astra Militarum analysts suspect that the T'au have somehow created the Torment, an impression hardly reduced by the Kroot mercenaries appearing in the employ of the death cult. Whatever the Gilded Torment really wants, the fight against the cult is a bitter and hateful one. The Astra Militarum mounts asteroid-hopping operations where each new planetoid is assaulted in lethal thin-atmosphere, low-gravity conditions.
Ravacene (Death World): Ravacene is a volcanic jungle-covered world within the Canis Salient. Ravacene's ecology is based on the volcanoes covering its single, planet-wide continent. The toxic ash spewed by these volcanoes feeds the dense, black-grey jungles covering its plains and valleys. The jungles proved resistant to the most enthusiastic attempts to burn or defoliate them.
The world was heavily contested by the Imperium and the T'au Empire's Kroot forces. For the troops of the Astra Militarum, few assignments were less welcomed than a posting to Ravacene. The ash-choked forests of this world are said to have given the Greyhell Front its name, and the Imperial Guard battling to wipe out the Kroot on this world fight a bleak, horrific battle against the planet and their alien foes alike. Ravacene chewed through Astra Militarum regiments at an appalling rate. Only Death World veteran regiments could expect to last more than a few solar weeks before being withdrawn. It is highly unlikely than any humans are still alive on the surface of Ravacene.
The Astra Militarum's objectives on Ravacene were simple. Ravacene was ideally placed to act as a staging post for a push into T'au space in the Reach, and its several moonlets would make ideal orbital dockyards for the voidships of the Imperial Navy. Before the planet could be used in this way, the Kroot presence on its surface had to be exterminated. The nature of the terrain means that this had to be carried out on the ground by, one Kroot at a time, no matter how many Guardsmen it takes.
For their part, the Tau simply wished to deny the Imperium use of Ravacene, so they deployed vast numbers of Kroot. These foul Xenos mercenaries evolved during their time on the world to match the ash jungles of Ravacene through the use of their ability to alter their genomes by ingesting other species' DNA. There could still be a considerable number of Kroot on the surface.
Veren (Feral/Xenos World): Veren was a human-inhabited Feral World under the "protection" of the T'au Empire's Velk'Han Sept. For reasons that Imperial forces could never ascertain, the Tau were very interested in keeping the Imperium from conquering Veren. The planet, a world of glassy black mountains and shallow oceans teeming with corals and algal blooms, is of little obvious strategic value.
Stable Warp-routes from the vicinity of Veren end at the Black Reef, so the planet would be of no use for staging an attack on Tsua'Malor. Nevertheless, the expeditionary force sent to scout the world was immediately opposed by Tau Hunter Cadres attacking in force.
Lord Commander Sebiascor Ebongrave was convinced that something important was hidden on Veren. Sending so many Tau to defend it proved its importance in his eyes. His analysts tried persuading him otherwise, that it was a trick of the Tau to draw attention away from other, more important battles. But the Lord Commander would have none of their cowardice. Ebongrave ordered Veren to be captured and held, but the T'au knew the planet very well, and defended it with great skill and determination. Although the Imperum's forces eventually gained the upper hand, the world was never truly conquered.
