Legio Praesagius - "The True Messengers" - Long allied to the warriors of Ultramar, the Legio Praesagius deployed to Calth at full Legio strength, with nearly 118 god-engines landed in the southern continent of Ithraca prior to embarkation. Mark of Calth is the twenty-fifth volume in The Horus Heresy series of novels and is an anthology of short stories.

Coordinated, they could achieve more than if they continued to fight alone and unsupported. In any other circumstances, Calth would have been declared lost to the Traitors, but the XIII th Legion's fierce resolve prevented them from giving into despair. Roboute Guilliman believed that the situation could be salvaged and the Word Bearers made to pay a price that they had not expected. In addition to Legiones Astartes assets, a great mass of cultic auxiliary units that accompanied the Word Bearers which may have numbered in excess of half a million men-under-arms, though the proficiency and sanity of most was questionable: Xana Incursion • Carnage of Morox • Sangraal Campaign • Liberation of Numinal • Battle of Arissak • Battle of Perditus • Battle of Sotha • Scouring of Gilden's Star • Battle of Nyrcon • Battle of Tallarn • Battle of Nocturne • Battle of Pluto Over a million soldiers the Imperial Army were mustered for the planned Ghaslaskh Crusade, including several established army groups such as the Calaq War Host, and nearly a dozen newly raised regiments from the various cities and agricultural provinces of Calth. Also added to the muster was a number of Solar Auxilia pattern regiments in anticipation of void actions against Ork asteroid-craft at Ghaslakh, including the much renowned 41 st Espandor High Guard. Other notable regiments include: This anthology contains the following stories: The Shards of Erebus by Guy Haley, Calth That Was by Graham McNeill, Dark Heart by Anthony Reynolds, The Traveller by David Annandale, A Deeper Darkness by Rob Sanders, The Underworld War by Aaron Dembski-Bowden and Unmarked by Dan Abnett.Comprising the majority of the XIII th Legion's Destroyer assets, and the stores of volatile and hazardous weaponry that characterised their operations. The 22 nd Chapter, known as the " Nemesis" Chapter, was often deployed in small formations alongside other chapter units. At Calth, 2,000 Nemesis Legionaries were mustered along the desolate Thrascias Highlands, furthest from the densely populated cities of Calth:

Suddenly the Primarch’s attention was diverted when he looked below their position and saw half a dozen surviving Word Bearers carrying the bloody carcass of Kor Phaeron. Somehow, the wretched First Captain of the XVII th Legion remained alive despite the fact that Guilliman had torn out his primary heart. Drawing their Bolters, the Ultramarines fired upon the retreating Word Bearers, just as their forms shimmered and vanished in a cascade of teleporter energy. Gathering at Saturn those of his Legion who had been embarked on crusades in distant parts of the galaxy, Roboute Guilliman would depart the Sol System mere months before news of Horus' rebellion reached the Emperor's ears. The turbulent state of the Empyrean in those years would see the Ultramarines' main strength journey to Calth by a winding and obtuse trail which would also cloak them from all attempts by Terra to recall them or forewarn them of Horus' actions. The Word Bearers, delayed by the slaughter at Istvaan, would not arrive at Calth until the majority of the XIII th Legion had already gathered, travelling a path of blood and ashes of their creation. As a result of the devastation wrought by the Word Bearers during the Calth Atrocity upon the Veridia System's sun, future generations of Calth's people were required to live deep underground in massive subterranean hive cities to escape their world's radiation-scorched, airless surface. As did all of us, my brother or sister, specified Horus. It distresses me to specify these indicate you, yet they ought to be specified, momentarily of battle is coming, absolutely nothing can avoid that, along with I require my closest brothers alongside me when the moment pertains to remove our Myriads of those that will definitely not follow us.The crux of the campaign came on the Agri-world of Calth in the Ultramar Sector, where the Ultramarines successfully broke the Word Bearers' surprise assault after a viciously-fought siege action, though at the cost of terrible casualties and the complete destruction of Calth's atmosphere and once-verdant biosphere. The situation outside was rapidly deteriorating as armoured columns in service to the Word Bearers moved into position and began firing at the Loyalists with a hail of shells and laser fire. Two Traitor Reaver-class Titans approached at full stride, intent on annihilating the servants of the Emperor. With the majority of his allied commanders already dead, Ventanus knew that his company line was all but broken. Embattled Ultramarines survivors take refuge in the caverns beneath Calth's surface as the Underworld War begins.

I The Solar War • II The Lost and the Damned • III The First Wall • Sons of the Selenar • IV Saturnine • Fury of Magnus • V Mortis • VI Warhawk • VII Echoes of Eternity • Garro: Knight of Grey • VIII The End and the Death ( Volume I • Volume II • Volume III) Then the angel took up the censer and filled it with fire of the altar and cast it down to the land; and there followed earthquake, thunder, lightning and death." Aeonid Thiel, Sergeant, 135 th Company [marked] - Thiel's helmet was painted red to indicate that he was marked for censure for running theoretical scenarios for combating other Space Marines - at the time, this was to satisfy his own curiosity and a yearning to account for all possibilities. However, due to the substantial losses amongst the XIII command personnel, Thiel emerged as a proficient leader and resourceful fighter. When the time came to organise the shattered remnants of the XIII into fighting squads, the new leaders were marked with the red helmet. This pattern continues to the present day. Mark of Calth takes place during the Battle of Calth and the Underworld War that followed. The Horus Heresy came to Calth without warning. In just a few solar hours of betrayal and bloodshed, the proud warriors of the XIII th Legion -- Roboute Guilliman's own Ultramarines -- were laid low by the treachery of their erstwhile brothers of the XVII th Legion, the Word Bearers. My brother, hear me. Warriors of the XVII th Legion, hear me. This violence is against the code of the Legiones Astartes and against the will of our father, the Emperor. In the name of the Five Hundred Worlds of Ultramar, I implore you to cease fire and stand down. Open communication with me. Let us speak. Let us settle this. This action is an error of the most tragic kind. Cease fire. I, Roboute Guilliman, give you my solemn pledge that we will deal with each other frankly and fairly if these hostilities can be suspended. I urge you to respond."

Contents

While the remnants of the Ultramarines and the Imperial Army were making their exodus to the caverns beneath Calth to escape the irradiation of the world's surface, the Ultramarines' 21 st Company, under the command of Captain Erikon Gaius, were dug in at one of the railway tunnels leading to Numinus City. Roboute Guilliman — Primarch of the XIII Legion ' Ultramarines', Lord of the Five Hundred Worlds, now know as 'the Avenging Son

Of the forces of the Excertus Imperialis, details are more vague, but it seems likely that at least half a million troops-under-arms perished during the fighting, alongside the entire fighting complement of the Legio Praesagius.Ventanus became a senior adviser to his Primarch, Roboute Guilliman, and helped to codify the strategies and dogmas of what would become the Codex Astartes. And in the 41st Millennium, his vengeful spirit assisted a certain Uriel Ventris to inflict a true death on the Word Bearers Daemon Prince M’Kar. The war on Calth continues both above and below ground. Ventanus, the "Saviour of Calth", attempts to destroy a large contingent of Word Bearers, but falls into a trap that may destroy all life on Calth. The Heresy came to Calth without warning. In just a few hours of betrayal and bloodshed, the proud warriors of the XIIIth Legion – Guilliman’s own Ultramarines – were laid low by the treachery of their erstwhile brothers of the XVIIth. Now, as the planet is scoured by solar flares from the wounded Veridian star, the survivors must take the fight to the remaining Word Bearers and their foul allies, or face damnation in the gloomy arcology shelters beneath the planet’s surface. The Primarch's intervention saved the lives of dozens of his sons. It fell to them though to persuade their gene-father to cease his furious battle on the flagship's outer hull and to rejoin his warriors within. The Primarch had fought for ten hours without respite, his sons believing him lost. Now he was returned to them, and for the first time since the beginning of the Battle of Calth, defeat and extinction did not seem inevitable.