Numinal is one of the few Agri-worlds located in the Coronid Deeps Sector, in the Coronid Reach region, within the Segmentum Obscurus at the very edge of the dark frontier of galactic space. Colonised in the late 890s.M30 as part of the nascent Imperium of Man's expansion efforts to further secure the region's food supply and navigational channels, Numinal formed an important link in the chain of human civilisation in the northern Imperium, as it had access to several recently discovered stable Warp routes through the region.
These routes linked it to the Manachean Commonwealth, the Agathon Domain on the frontier to the galactic North, and the Cerada Trinity and the minor independent Imperial colony systems of Vespasia Infernus and Garella which made up the rest of the Coronid Reach.
This network of Warp routes at its most extreme offered potential further access to several important worlds far out on the Eastern Fringe of the Imperium which could not normally be journeyed to without potentially many sidereal months of continuous travel via the illusive Hadexus Warp Channel, which reaches out as far as the Angelis and Honourum Systems. These vital routes made Numinal a prime target in the civil wars which wracked the Coronid Reach in the aftermath of the main Traitor attack during the Horus Heresy.
As such, Numinal forms the proverbial gateway to the Coronid Reach. Its exports almost exclusively flow to the densely populated world of the Manachean Commonwealth where they feed billions of inhabitants. The world suffered greatly during the dire events of the Horus Heresy as it was occupied early on in the conflict by forces of the Cyclothrathine Mechanicum. The Imperial counter-invasion led by the Agathean Cohorts under the esteemed Lord Marshal Ireton MaSade has since entered history as the lauded Liberation of Numinal.
Numinal is a terrestrial-type Agri-world of the oceanic sub-type which has commonly been called an Ocean World. It is a planet of world-spanning oceans and numerous volcanic archipelagos and islands, the largest of which form Numinal's principal continent. Numinal's late discovery occurred when Imperial Explorator Fleets followed the stable Warp-routes originating from the Manachean Commonwealth which had just been recently liberated from the baleful overlordship of the Mitu Conglomerate. Since then, Numinal has formed an important link in the chain of human civilisation in the northern Imperium.
With the discovery of several stable Warp-routes linking it to the future Agathean Domain and the Cerada Trinity, Numinal's exploitation as an Agri-world was quickly decided. As would later be discovered, these stable Warp-routes extended far into the Eastern Fringe of the Imperium, reaching as far as Honourum -- future homeworld of the Novamarines Space Marine Chapter -- and lost Angelis in the Ultima Segmentum, permitting starships to bypass entirely the illusive Hadexus Warp Channel on which plenty of voidships had already been lost. These vital routes would make Numinal a prime target during the civil wars that would follow the main Traitor attack during the era of the Horus Heresy known as the Age of Darkness, but at the world's beginnings, these proved a boon for the nascent Agri-world.
Segmentum authorities had placed high hopes in this planet and when Imperial colonisation began in the late 890s.M30, it was almost achieved within a standard decade. Rapidly constructed prefabricated cities and outposts soon harbored some forty million inhabitants while a navigational beacon was installed on the habitable moon of Numinal V, henceforth known as Quachil. Numinal's saline seas had been given over to aquaculture and epigenetic engineering by specially despatched Magi Biologis retinues which would further improve Numinal's native or imported fauna and flora. To exploit these natural resources, well-developed orbital trans-shipping infrastructure and an immense geo-synchronous void–station were constructed. Almost immediately after completion, Numinal began with the export of nutrient-rich compounds -- mostly algae and fish -– for the densely populated worlds of the Manachean Commonwealth.
Numinal's oceans had, however, not been entirely bereft of intelligent life, as the presence of several primitive amphibious and ichthyoid species native to Numinal warranted suppression and extermination campaigns led by specialised units of the 1023rd and 2774th Obed Cohorts of the Exertus Imperialis. These Solar Auxilia veteran cohorts as well as a native detachment of Solar Auxilia security forces were stationed on board Numinal's void station and were the only standing military forces when the entire region was overcome by the first battles of the Horus Heresy in 007.M31.
The attackers were not Traitor Legiones Astartes, but Cyclothrathe-bound Battle-Automata. Against this preternaturally relentless foe, organised resistance proved difficult and shortly after the void station had been taken, the only Loyalist military forces remaining on Numinal were those of the Obed Cohorts. The remnants of these Cohorts quickly splintered into a resistance guerrilla force which used their expertise in the swamps and semi-aquatic terrain that dominated Numinal to their advantage.
The terrain was anathema to the Mechanicum's heavier units such as Castellax and Thanatar-class Battle-Automata, while the lighter units could often be ambushed through the Obed Cohort's knowledge of the surrounding lands. The Obed Cohort's efforts were focused on sabotage and opportunistic assaults, a campaign they maintained for an entire Terran year and required further Mechanicum reinforcements to quell.
This forced the Cyclothrathine Mechanicum to redeploy troops it had originally intended for other warzones and after the continuous failings of the local Magos, it became clear that the Cyclothrathe's principal warlord, the vaunted Archmagos Yelav Draykavac, needed to be recalled from the frontlines in the Cerada Trinity to deal with the matter.
Still the Obed Cohorts could not readily be drawn into combat and eluded every attempt at a pitched battle which would soon have seen them crushed against the superior Mechanicum forces. Tired of chasing this illusive target, the ruthless Archmagos would devise a different strategy: if he could not destroy the Obed Cohorts, he would destroy what they had been protecting.
Probably intended all along, Archmagos Draykavak ordered the forcible conversion of Numinal's civilian population into Mechanicum-bound Servitors or Adsecularis Troopers. This would serve two purposes, first to increase his own forces as well as diminishing the supposed Loyalist population which the Obed Cohorts used for shelter and resupply, and second forced the Obed Cohorts to make a stand, their sense of duty compelling them to take action against this most vile practice of the Dark Mechanicum. In this second matter, Draykavak's plan would function perfectly; however he could not have predicted that this action would take place during the famed Liberation of Numinal.
- The Horus Heresy - Book Four: Conquest (Forge World Series) by Alan Bligh, pp. 38, 42, 54-57, 61, 63, 74-75