Spiritus is a renegade organization that focuses its efforts on further understanding, and eventually gaining mastery of the Warp. Part of a greater umbrella organization known as the Vitores Tenebras, whose broader goal is to create a revolution within the human race, Spiritus seeks to grant humanity its ascendence by harnessing the Psychic energies of the Warp to their full potential. They are lead by Edrith Cambion, a former Inquisitor Lord of the Ordo Malleus and their founder. Spiritus is small and isolated even within the Vitores Tenebras. This is a product of Cambion's will, for he believes that few within the wider organization of the Vitores Tenebras could handle the work that Spiritus devotes itself to, and more importantly because he has secrets that he feels compelled to obscure from his fellows. While Spiritus lacks scale in size and activities by comparison to the two other primary divisions of the Vitores Tenebras, it dabbles in dark forces that can devour the soul and tear the skin of reality asunder, making them just as much a threat as their peers.
While Spiritus technically came into being at the same time as the rest of the Vitores Tenebras, its foundations had been laid far before Edrith Cambion ever met his two co-conspirators. As Edrith found himself going down the path of the Radical he began to look for kindred spirits. He looked for those that shared his fascination with the world beyond our reality, and that shared his vision for its place in humanity's destiny. Along with those followers that aided in Cambion's inquisitorial work in a practical manner, Edrith began to recruit various other specialists into his staff. These specialists included scholars who had made the Warp or psychic power their primary fields of study, Psykers with rare psychic disciplines, some of which were apostate, and those that had directly interacted with Daemons and the Warp and had been changed by the experience. This gathering of unique individuals formed Edrith's extended retinue, and would form the core of Spiritus when Cambion finally abandoned the Imperium for his own purposes.
As Cambion broke away and began to begin his clandestine activities as a Tenebrous One he expanded his small band of specialists and followers into the large operation it is now. The newly formed Spiritus began to actively and effectively scour the stars for Psykers to recruit to their cause, as well as for warp-lore and psychic artifacts. In a very short period of time Spiritus became the Vitores Tenebras' formost resource when dealing with psychic assets and threats. However Spiritus remained somewhat isolated from its sibling branches. Cambion believed that the knowledge and forces that they were dealing with were too dangerous to allow into the hands of the unworthy, and while he had fiath in the abilities of Cutler Kar and the Magister, he was concerned that some of their subordinates would be injcapable of handling the proscribed lore that he was developing and uncovering. As a result Spiritus operated under an even thicker veil of secrecy than Animus and Corpus. This highly insular nature may be one of the reasons why Edrith became corrupted, as his partners might have better noticed his deterioration if he had maintained greater contact with them.
Edrith had skirted the edge of damnation for years. Despite openly dabbling in Chaotic forces he had always managed to maintain his since of purpose and vision, never truly falling under their influence. However this changed shortly after he began working as a Tenebrous One. Edrith now had access to lore and tools that he had never dreamed of before, and he had free reign to deal with these forces as he saw fit. He began to delve into lore and arts that he would have never dreamed of touching while he was still part of the Inquisition. To make matter worse, while Edrith himself seemed to be able to hold on to his sanity some of his closest advisors proved more susceptable to corruption. These damned confidants began to urge Cambion to take greater risks, and embrace more fully the dark secrets that he held. Inevitably the influence of Chaos took hold of Edrith, and he became a wholeheartedly devoted to the cause of Chaos. He corrupted what was left of his direct subordinates, and hid the corruption of Spiritus inner circle from the rest of the branch, and from the Vitores Tenebras in general. Spiritus was now run by a secretive Chaos Cult, unknown to both the bulk of the branch and its umbrella organization.