In the 35th Millennium, Tigrus was overrun by the WAAAGH! of the Warlord Arrgard the Defiler and was held under Ork dominion for several millennia. This was a stain on the honour of the Mechanicus, who refused to let this important bastion of the Machine God remain in the greenskins' vile hands.
At some unknown point in Imperial history, Tigrus was eventually brought back into the Imperial fold, reconsecrated, and once again became a vital Forge World of the Imperium.
The early history of this vital Forge World has been lost across the millennia. Originally a part of the Realm of Ultramar when it still comprised a stellar empire of five hundred worlds in the time of the Great Crusade, Tigrus was responsible for the design and manufacture of several patterns of heavy weaponry utilised by Imperial armoured vehicles as well as small arms for the elite Legiones Astartes.
For almost five standard millennia following the Horus Heresy, Tigrus continued to play an important role as a prosperous and strategically-vital Forge World within the Segmentum Ultima. But at some point during the 35th Millennium, Tigrus fell to the ravages of the rampaging Ork WAAAGH! Arrgard. The forces of the Imperium attempted to take back Tigrus from the savage Greenskins several times over the intervening millennia, but almost every campaign fell short and Tigrus remained an industrious Ork World. Eventually, this stain to the Mechanicus' honour was finally rectified, and Tigrus was brought back into the Imperial fold.
- The War of Neotech (Unknown Date.M41) - The T'au settlers of Vesh'yo find themselves fighting for their lives against three Skitarii Legions. The ancient weapons of the Adeptus Mechanicus are pitted against the clean, cutting-edge technology of the T'au Empire. Many additional Skitarii reinforcements are deployed before victory is finally secured. Six star freighters full of T'au war materiel find their way back to the Forge World of Tigrus.
The Fellblade Accelerator Cannon was a Cogitator-assisted high velocity weapon designed on the Forge World of Tigrus. The Accelerator Cannon was a superior heavy armament able to switch between high-density armour-piercing shells for use against enemy armour and fortifications, and powerful high-explosive fragmentation rounds more suited to assaulting large concentrations of infantry.
Tigrus was also known for the development of the more sophisticated Leman Russ Vanquisher battle tank. Once a common sight wherever the Imperium's armies fought, it became increasingly rare as the skills and technology required for the construction of its long Vanquisher Cannon were lost when the Forge World of Tigrus was overrun by WAAAGH! Arrgard. Such is the power of this gun and the sophistication of the weapon's ammunition there is no known armour a Vanquisher Cannon cannot penetrate, and even the thick battle-plate of Titans has been known to be punctured by a direct hit.
Since the loss of Tigrus, the Tech-priests of the Adeptus Mechanicus made strenuous efforts to reproduce the design by reverse-engineering surviving Vanquisher Cannons, but met with limited success. With Tigrus restored to the Imperial fold, the manufactoria ring out once more with a continuous din, as this vitally important Forge World is once again able to produce a weapon that is desperately needed by the military forces of the Imperium.
Once the cutting edge of Battle Cannon technology, the anti-armour Hunter Shell was developed on Tigrus and only ever produced on that Forge World; the knowledge of its construction was lost with Tigrus' capture by the Orks. A few shells are occasionally found in storage and issued to Imperial forces, but the vast majority of Astra Militarum tank crews will never see a Hunter Shell, let alone fire one.
The Hunter Shell is considered blessed by the Machine God by those who have the good fortune to be issued with it. This is due to a small logis engine that has been implanted within its casing, similar to that used in a Hunter-Killer Missile, which directs the shell's trajectory after firing. Upon locking onto a target, it will track its movement, and steer the shell along a ballistic path that allows it to drop down atop the vehicle where the armour is often weakest.
Tigrus is also notable as a long-time developer of weapons for the Adeptus Astartes, which included the mighty and iconic Bolter. During the final days of the Great Crusade, the design for the Tigrus Pattern Bolter was first discovered in the depths of Forge World Tigrus. The STC data for this sleek weapon was disseminated throughout the Imperium before the outbreak of the Horus Heresy.
Tigrus Pattern Bolters continue to see service in the late 41st Millennium, and they are revered and honoured by their wielders as ancient relics of Mankind's lost glory. Though one of the rarer patterns of Astartes weaponry, Tigrus Pattern Bolters are renowned for both their accuracy and the easy facility of their Machine Spirits in coordinating with the systems incorporated within Space Marine Power Armour.
- Codex: Adeptus Mechanicus (8th Edition), "Bastions of the Machine God," "The Quest for Knowledge," pp. 13, 34
- Imperial Armour Volume One - Imperial Guard & Imperial Navy, pp. 8, 31
- Imperial Armour Volume One: Second Edition - Imperial Guard, pp. 10, 18, 237
- The Horus Heresy - Book One: Betrayal (Forge World Series) by Alan Bligh, pg. 224