Cadia - Post-Heresy: Following the Siege of Terra that ended the Horus Heresy with Horus's death and the interment of the Emperor of Mankind in the Golden Throne, the defeated Traitor Legions and their allied forces among the Imperial Army and the Dark Mechanicum fled from Terra. Some of the exhausted Loyalists rallied and gave chase, but most remained on Terra to consolidate their great victory over the forces of Chaos.Many of the surviving Traitors were put to the sword, but the majority of the Traitor Legions escaped into the great Warp rift known as the Eye of Terror in the Segmentum Obscurus, a region of space where reality and the insanity of Chaos collide as the raw psychic energy of the Immaterium pours into real space-time.Within the Eye of Terror, the Chaos Gods rule over uncounted numbers of planets, all warped to reflect their own dark aspects. It was there that the Traitor Legions found refuge, isolated from the rest of the galaxy by potent Warp Storms. Each of the planets within the Eye is a Daemon World, warped and twisted by the whims of the Ruinous Powers and the powerful Daemon Princes who rule over them in the Dark Gods' name.The Chaos Space Marines regrouped and nurtured their hatred of the Imperium, planning for the day when they would wreak a terrible vengeance on those who had defied them and their foul masters. Within the Eye time flows differently than in realspace.Those same Traitors who fought on Terra 10,000 standard years ago still fight today in the service of Chaos. They fight against each other to prove their supremacy and against the forces of the Imperium when the Warp Storms calm enough to allow them to emerge into Imperial space.The Imperial sectors surrounding the Eye of Terror were heavily militarised to resist these frequent invasions and none more so than Cadia, the Imperial Fortress World that stands at the very mouth of the only stable navigational route leading out of the Eye of Terror, the dreaded Cadian Gate.As a result of Abaddon the Despoiler's 1st Black Crusade in 781.M31, the planet's strategic location was deemed vital to the defence of the Imperium, and so, in the 32nd Millennium, Imperial colonists were despatched to resettle the world, becoming the ancestors of the present-day population of Cadians. Perhaps as a result of the Eye of Terror's proximity, this later population of Cadians also soon developed the unusual violet-coloured eyes that had marked the first human inhabitants of the planet.The early defences of the newly resettled Cadia proved to be woefully inadequate. Its major cities were extremely vulnerable to enemy assault as they had been constructed in the traditional High Terran style, with broad, ordered avenues. Following the 2nd Black Crusade in 597.M32, sweeping changes were carried out worldwide to improve the planet's overall defensive capabilities, and massive fortifications were constructed across the world until the planet's cities had been rebuilt into their current form.Cadia stands upon the only known reliable route out of the Eye of Terror and thus is one of the most strategically vital worlds in the entire Imperium of Man. There are other routes out of the Eye, but none are stable like the Cadian Gate and no military force of any true size can venture forth from the Eye without first passing through it. The exact reasons for the existence of this unusual region of stability is unknown, though many Magi of the Adeptus Mechanicus believe it is due to the presence of the famous Cadian Pylons.These mysterious black monoliths, now known to have been created by the Necrons millions of standard years ago to hold back the psychic influence of the Warp that was so feared by their C'tan masters, dot the landscape of Cadia. Their origins remained mysterious to the Imperium until the time of the 13th Black Crusade.Cadia itself was a bleak, merciless and wind-blown planet, where only the strongest survived to adulthood and discipline was learned from the moment a babe took his or her first steps. Cold winds howled across wide, sundered plains where armies trained with live ammunition and every solar day not spent training was believed to be a day wasted. Every Cadian fortress-city, or "Kasr," was a massive citadel, with the streets and buildings fashioned with great tactical cunning by the finest military engineers and siege specialists of the Astra Militarum.Every Cadian was taught the skills of the warrior as soon as he or she could walk and Cadians were much sought after by commanders throughout the galaxy. Cadian military gear is considered top-rate and is used as the base standard for all Astra Militarum regiments. Such a world bred hardy and determined warriors and the Cadian Shock Trooper Regiments of the Astra Militarum have a well-deserved reputation for both honour and fighting spirit. From the earliest ages, Cadians were taught to field-strip a weapon with their eyes shut and tactical doctrine was memorised before basic literacy.