High; In the tens of billions
Mordian is an Imperial Hive World in the Segmentum Obscurus that is the homeworld of the Imperial Guard's Mordian Iron Guard regiments. Many of the Imperium's enemies have underestimated these ranks of colorfully-uniformed troops, only to find out that they are among the toughest and most uncompromising of the Emperor's soldiers. The people of Mordian are often of a dour and grim temperament, living as they do in perpetual darkness. The suicide rate on the planet is reportedly now the highest in the Imperium since the destruction of the Night Lords Traitor Legion's homeworld of Nostramo. Mordian also once came under a great assault by the Forces of Chaos that was defeated only through the extraordinary discipline and valour of the Iron Guard in one of the Imperium's finest moments.
Mordian is a world that is tidally locked with its star, so that the Mordian day is the same as the Mordian year. As the planet does not rotate on its axis this means that like Luna, one-half of the planet is bathed in perpetual darkness and the other half burnt to a cinder by the glaring sun. This unusual planetological characteristic makes Mordian a truly miserable world to live upon, and it has well-earned its moniker as the "World of Eternal Night" as all of the human settlements on the world lie on Mordian's dark side. The planet's lack of rotation prevents any strong winds from developing due to the lack of a Coriolis Effect and as such the atmosphere is thick and dark. The world's billions of human inhabitants live in vast hive cities where all resources are controlled and distributed by the Mordian state. Mordian's hundreds of millions of inhabitants live on a land surface barely one tenth the size of Terra. Its hive cities are characterised by pyramidal, multi-levelled towers rising like mountains of steel and ceramic towards the ebon sky. The planetary government of Mordian is known as the Tetrarchy, and it strictly controls and rations the planet's meagre resources. This scarcity and authoritarian repression naturally breeds discontent, and the existence of the Iron Guard is often the only thing that stands between order and total anarchy. There is much discontent among the people, and the Imperial Guard regiments raised from Mordian, the Mordian Iron Guard, spend much of their time simply keeping the populace in line when they are not deployed to Imperial war zones.
Battle of Mordian
In the long and sinister annals of the Inquisition there are many tales of treachery and horror, of the destruction of worlds and the triumph of man's greed and foolishness. It is a record of human weakness and the power of the Chaos Gods. Yet amongst the record of lost planets and mortal defeat there are a few stories of human victory -- rare cases where the daemonic army of Chaos has been turned aside at the moment of success and driven back into the void from which it came. Mordian is one such world. The greatest threat to Mordian came one hot summer. The stifling heat was unusual even for Mordian, and the planet seethed with unrest. Beneath the streets brooded a secret conspiracy that posed a threat far greater than any seen before. In the depths met a dark conclave, a group of men who knew the extent of Mordian's wealth and wanted it for themselves.
Away from the sight of saner citizens they made their incantations and called upon the Dark Gods of Chaos. A spell was begun. It is impossible to say how much innocent blood was spilled to fuel their sorcery, or what sinister pledges were made to their dark masters. Those who cast the spell sought only personal enrichment; their lust for power knew no bounds. They would destroy the planet itself if they had to. They cared no more for its teeming millions than did the Chaos Gods. The summer grew hotter as the spell neared its completion. Many strange things were reported in the capital city of Vanandra. The cannibal mobs and criminal gangs were restless. Men saw winged monsters hovering in the city lights. People disappeared without a trace.
At last the spell was complete and suddenly the world shook as its sky erupted into flame and disgorged the Warlords of Chaos itself. From the Eye of Terror distorted and ugly spacecraft soared into the Mordian skies to rain fire and destruction upon the world. Chaos Space Marines poured into the city slaying all around in a great and bloody sacrifice to their gods. Daemons stalked the burning towers and hunted the souls of those that fled from the devastation below. From their dark hiding places the servants of Chaos crawled to the surface to bathe in the fire and terror of the world, confident of their masters' favour now that their work was done.
As the sky exploded into flame, the Tetrarchs of Mordian ordered their Astropaths to send psychic calls for help. The power of Chaos was so strong that the Astropaths' minds melted with the effort. It was impossible for anyone to say whether the messages got through or if help was on its way. Meanwhile, the Iron Guard fought a gallant resistance against the daemonic assault. Whilst lesser men fled in terror before the might of Chaos, the Iron Guard stood their ground, pouring volley after volley of laser fire into the enemy's ranks. At last the Iron Guard captains were forced to give the order to withdraw. Though their men would stand until the end, they could achieve little against the hordes of daemons and superhuman Traitor Marines that opposed them. Reluctantly the Iron Guard regrouped around the capital, abandoning the rest of the planet to the enemy.
Whilst the forces of Chaos rampaged throughout Mordian, the Iron Guard prepared Vanandra's defences. Every building became a fortress, every tower a strongpoint, and every street and plaza a killing-zone for the Iron Guard's carefully sighted weapons. At the centre lay the Tetrarchal Palace itself, from which the defence of the capital was coordinated. When the attack began, the Iron Guard was well prepared. Chaos Space Marines fell before their well-disciplined fire as shot after shot struck their ranks. Channelled into well prepared fire traps the Chaos Marines were easily repelled, but far greater and more potent foes followed upon their heels.
From the sewers and service ducts of the capital poured an army of Chaos Cultists, those wretches who had sold their souls to the Dark Gods. Clad in rags and armed with no more than iron bars and lengths of chain, they threw themselves upon the defenders. Driven by their insane devotion to Chaos, they cared little if they lived or died, and thousands were cut down by the devastating weapons of the Iron Guard. Nonetheless, this attack from an unexpected source left the defenders unprepared for the next assault. The Forces of Chaos moved upon the Iron Guard with purpose. Daemons and Chaos Space Marines advanced as one. Bloodthirsters of Khorne roared a great challenge to chill mortal blood. Keepers of Secrets stalked the battlefield, slaying those that dared to look upon them with a withering glare. Whirling Horrors skipped and chattered in an eerie blur of incandescent power. It was a terrifying sight, yet the Iron Guard held firm before the onslaught though many paid the ultimate price for their devotion.
Street by street, building by building, the Iron Guard fell back into the heart of the city. Their lines drew tighter but refused to break, as attack after attack was repulsed. When losses grew too heavy to endure, or as positions were outflanked and became untenable, the Iron Guard withdrew to another line, always preserving what they could of their men and weapons. It was a battle fought with all the tactical brilliance and discipline the best Imperial troops could hope for. Yet it was a battle the Mordians could not win. Eventually they would have nowhere left to retreat. At last the Iron Guard took position around the Tetrarchal Palace itself, the last strongpoint on the whole world. Behind hastily constructed defences the infantry waited for the inevitable attack. From the towers and ceremonial balconies the barrels of Lascannons and other heavy weapons glinted in the light of the burning sky.
Suddenly the horde of Chaos was upon them, screaming and bellowing in its might. Greater Daemons of Nurgle strode clumsily amongst their minions, rising above them four or five times the height of a man, giants and lords of their foul kind. The bloated daemons shuffled forward, putrid innards spilling over the ground, nauseous gasses bubbling from rents and tears in their leathery flesh. Beside them were the Plague Marines of the Death Guard, wholly dedicated to that pestilential god, their armour green and rancid with decay, their rank bodies stiff with disease. Before them came a black cloud of flies which buzzed about the Iron Guard, crawling into their eyes and ears, and filling their mouths with black hairy bodies.
The Iron Guard's Lasguns spat a volley of death into the screaming horde. Again the Lasguns cracked with a single voice, as the captains ordered shot after shot into the vile mass. From the Tetrarchal Palace came the chatter of Autocannons, the angry scream of Bolters and the piercing shriek of Lascannons. With mechanical precision the weapon crews loaded and fired over and over again, never stopping for one moment or breaking their routine. Daemon gore ran like a foul river in the once-white square, but as one beast fell another twice as hideous marched over its body toward the Iron Guard's position. The captains ordered their men back to the palace steps and formed a firing line. Their discipline intact, the Iron Guard prepared for a single volley before the Forces of Chaos fell upon them. Their final moment had come, though there were few left now to witness their inevitable defeat.
Little could the defenders of Mordian know of the power or purposes of Chaos, or that the Chaos Gods' hold upon Mordian was but a tenuous one. The spell that had brought them to mortal space and imbued the flesh of their servants with physical energy was almost spent. The fires that burned in the sky grew dim and the bellows of daemons echoed shallowly in the air. As the Iron Guard watched, their enemies dissolved before their eyes. The sky darkened to its customary blackness. In the dark the guiding lights of Imperial spacecraft glittered amongst the stars. The Iron Guard had won not just a battle, but the most precious thing of all -- time. From beyond the orbit of Mordian, Imperial psykers had wrought a counter-spell to break the hold of Chaos. While the Iron Guard fought upon the planet, a separate battle of wills had raged between the mortals of the Imperium and the Dark Gods. Only the Iron Guard's heroic resistance had given the psykers enough time to work their mystical abilities before Chaos won the planet for all time.
The disappearance of their most potent units demoralized the remnants of the Chaotic attackers and the Iron Guard took the opportunity to rout the enemy and force them from the planet. Through their sheer discipline and willingness to lay down their lives in away that would have impressed even an Astartes, the Mordian Iron Guard had held back the Forces of Chaos long enough for the Imperial Sanctioned Psykers to break the spell, and ensure that Mordia would remain in the hands of the Imperium of Man.
As a result of the Battle of Mordia, the regiments of the Mordian Iron Guard were soon considered some of the most elite units of the Imperial Guard in existence and were deployed to multiple conflicts across the galaxy.
- Codex:Imperial Guard (5th Edition), pg. 16
- Codex: Imperial Guard (3rd Edition, 2nd Version), pg. 59
- Codex: Imperial Guard (2nd Edition), pp. 13-15
- Only War: Core Rulebook (RPG), pp. 52-53
- White Dwarf 154, "Mordian Iron Guard"