The Obsidian Depths
The Obsidian Depths of Velaraxis
The Obsidian Depths is a vast and mysterious network of subterranean caverns located deep beneath the surface of Velaraxis. These caverns are so named because of the dark, glassy volcanic rock that lines the walls, glistening eerily in the dim light. The tunnels were carved out by ancient volcanic activity, but over millennia, they have been expanded and modified by both xenos civilizations and, more recently, the Mechanicum during their mining operations. The Depths are filled with treacherous terrain, unknown dangers, and are rumored to contain ancient and forbidden xenos technology.
Geography and Environment
The Obsidian Depths extend for hundreds of kilometers beneath the planet’s surface, forming a labyrinthine maze of tunnels, caverns, and deep chasms. The rock formations are made of obsidian-like volcanic glass, which is both razor-sharp and unnaturally durable. In some places, the glass has formed intricate patterns that refract light in strange ways, making navigation difficult and disorienting. The walls and ceilings of the caverns are dotted with glowing mineral deposits that give off a faint, cold light, casting long shadows and adding to the sense of foreboding.
The environment in the Depths is inhospitable, with stagnant air and fluctuating temperatures that can plummet to freezing or rise to searing heat. Pools of toxic liquid bubble up from the depths of the planet, and the constant shifting of tectonic plates makes the ground unstable. Earthquakes are common, causing sections of the tunnels to collapse unexpectedly. The sound of grinding rock and the distant echo of shifting stone can often be heard, creating a constant sense of tension for those who venture into the Depths.
Historical Importance and Xenos Influence
Long before the arrival of humanity on Velaraxis, the Obsidian Depths were home to an ancient xenos civilization that vanished long before the rise of the Imperium. This civilization left behind remnants of their advanced technology, hidden deep within the caverns. The Mechanicum, during their mining operations, uncovered strange relics and artifacts within the Depths—some of which have been studied, while others remain dormant, their purpose unknown.
It is believed that these xenos relics could hold incredible power, capable of altering the balance of the war on Velaraxis. However, the xenos structures within the Depths are often protected by ancient, self-repairing defense mechanisms that still activate when intruders approach. These devices have caused the deaths of many explorers and Mechanicum teams, who were unprepared for the automated defenses.
Strategic Role in the War
The Obsidian Depths have become a key battleground in the ongoing war for Velaraxis. Both the Loyalist Mechanicum and the Dark Mechanicum, as well as the Space Marine Legions on both sides of the conflict, seek to control the Depths for the powerful xenos technology rumored to lie hidden within. The Depths also provide a network of secret underground passages, allowing forces to move undetected beneath the surface, launch surprise attacks, or bypass heavily defended areas.
Mechanicum Operations: The Loyalist Mechanicum has established small outposts within the upper layers of the Depths, where they have begun excavating the more accessible xenos relics. These outposts are fortified but constantly under threat from Dark Mechanicum raids and sabotage attempts. The Loyalists hope to unlock the secrets of the xenos technology to turn the tide of the war on Velaraxis.
Dark Mechanicum Presence: The Dark Mechanicum, drawn by rumors of forbidden technology, has also begun sending expeditions into the Depths. They are more willing to risk activating the dangerous xenos artifacts, believing that the Warp-infused power they may unlock could give them an overwhelming advantage. The Alpha Legion has allied with the Dark Mechanicum in the Depths, using the labyrinthine tunnels to strike at Loyalist forces and disrupt their mining operations.
Subterranean Warfare: The battles fought within the Obsidian Depths are brutal and claustrophobic. The narrow tunnels limit movement, and large-scale engagements are impossible, forcing both sides to rely on small strike teams, ambushes, and guerrilla tactics. The unstable terrain and constant risk of cave-ins add to the chaos, making even the smallest skirmishes deadly. Warhound Titans and other large war machines are ill-suited for the environment, making infantry and elite strike forces the key combatants.
Hazards and Challenges
Ancient Xenos Defenses: Deep within the Depths, the remnants of the ancient xenos civilization's automated defense systems remain active. These include energy barriers, laser grids, and even autonomous drones that attack any intruders. The defenses are highly adaptive, learning from previous engagements and adjusting their tactics accordingly.
Unstable Terrain: The volcanic nature of the Obsidian Depths makes the ground highly unstable. Tunnels can collapse without warning, and fissures often open up beneath the feet of unsuspecting soldiers. In some places, rivers of molten rock flow just beneath the surface, creating additional hazards for those traversing the tunnels.
Toxic Atmosphere: The deeper one ventures into the Obsidian Depths, the more toxic the air becomes. The atmosphere is filled with sulfurous gases and volatile compounds, requiring advanced filtration systems and protective gear to survive for long periods.
Psychic Residue: Some sections of the Depths emit a strange psychic presence, which can affect those sensitive to the Warp. These areas are believed to be linked to the xenos relics, though their exact purpose remains a mystery. Psykers entering the Depths have reported disturbing visions, hearing voices, and even losing control of their abilities.
Notable Engagements in the Obsidian Depths
The Battle of the Crystal Caverns: One of the largest engagements in the Obsidian Depths occurred when a force of Dark Angels and Imperial Fists launched an assault to reclaim a Mechanicum outpost from the Alpha Legion. The battle was fought in the Crystal Caverns, where massive crystalline structures refracted light and made visibility difficult. The Alpha Legion used the caverns' natural distortions to their advantage, ambushing the Loyalist forces at every turn. Despite heavy losses, the Loyalists managed to drive the Alpha Legion from the outpost, though much of the xenos technology had already been looted.
The Fall of Outpost X-34: One of the deeper Loyalist outposts, Outpost X-34, was overrun by the Dark Mechanicum in a surprise attack. The Traitor forces, led by corrupted Mechanicum forces, infiltrated the tunnels under the cover of a tectonic shift that caused massive cave-ins across the region. Outpost X-34 was lost, and with it, several valuable relics, which the Dark Mechanicum are believed to be studying for potential weaponization.
Future of the Obsidian Depths
As the war on Velaraxis intensifies, the Obsidian Depths will continue to play a critical role in the conflict. The hidden xenos technology and the network of tunnels provide invaluable resources and strategic advantages, making the Depths a focal point for the ongoing struggle between Loyalist and Traitor forces. However, the dangers of the Depths are not to be underestimated, and the toll of exploring and fighting in these dark, treacherous caverns continues to mount for all involved.