Anuaris is a major Forge World of the Adeptus Mechanicus located in the Ultima Segmentum. It was established within the fledgling Realm of Ultramar sometime during the Great Crusade in the mid-800s.M30, following the discovery of Primarch Roboute Guilliman on Macragge. At that time, there were as yet no Forge Worlds of the magnitude of ancient Accatran, with only Anuaris, still tied both in tribute and loyalty to distant Accatran as much as Macragge, and the reclusive Magi of the iron-bound moon of Gantz ranked as true Forge Worlds within the boundaries of Guilliman's fiefdom.
For unknown reasons, there was much animosity and acrimony between Anuaris and the Forge World of Konor, Gantz's sister world, in the form of an ancient feud between their Mechanicum hosts. This was most likely due to the favour and status Konor was shown by Guilliman as the seat of one of the five ruling Tetrarchs of Ultramar, such that it had ceded some part of its own authority to that of Guilliman on Macragge.
The Calth Conjunction and the Battle of Calth
When the call to arms for the Ghaslakh Campaign reached the Mechanicum enclaves of Ultramar sometime in 007.M31, the various magi were quick to see the logical advantage of combining their forces. Alone they would be subsumed into one or other of the Imperium's other formations and likely employed with minimal efficiency; together, acting as one body, they would operate at optimum capacity and prove a valuable military tool for the coming Crusade and the advancement of their own enclaves. Amongst the ranks of the Imperial Army or certain of the Legiones Astartes, such a decision would have prompted many solar months of posturing and political conflict as the various leaders sought one amongst them to lead, but this was not so among the warriors of the Mechanicum.
Yet the various Magi held on Macragge state that the resulting debate lasted for exactly fourteen solar seconds. Conducted entirely in the binary cant of the Machine Cult, the fraught negotiations granted primacy within the Taghmata Omnissiah to Archmagos Cronn Barbarel, due both to his eminent seniority and fealty to the lords of Gantz who remained neutral in the ancient feud between Konor and Anuaris. Only by deft compromise were the contingents of both Konor and Anuaris kept within the ranks of the combined Taghmata and even so, the Magi of Konor were to delay their arrival at Calth by several solar weeks over supposed disagreements that the muster order favoured the taghma of Anuaris over their own. Indeed, the forces of the Taghmata assembled from the various enclaves was amongst the last of the formations to arrive at Calth, with detachments from over a dozen individual worlds, moons and Monolith-class factory hulks from across Ultramar. When arrive they did, each was assigned a muster site as space became available amongst the teeming horde of Imperial military might assembled upon the surface of Calth, with taghma from the greater Taghmata scattered across the planet's surface.
The vast flesh-thrall hordes of Konor's lacyraemarta Adepts were assembled on the rolling plains of Barrtor alongside the Ultramarines 2nd and 16th Chapters and the armoured autokrator squadrons of the Anuaris taghma, the Magi at the head of those taghma being at pains to ensure that their old rivals would not seem more efficient than their own vassals as they stood in flawless ranks alongside the cobalt blue files of the Ultramarines. When the Battle of Calth began with the Word Bearers Legion's betrayal of the Loyalists and the revelation that it had sided with the Warmaster Horus, it was on the plains of Barrtor that the sacrifice of Anuaris armoured units engaging the onrushing Word Bearers allowed the remnants of the Ultramarines 2nd and 16th Chapters to pull back without being annihilated.
- The Horus Heresy - Book Five: Tempest (Forge World Series) by Alan Bligh, pp. 133-134