Psi-resonant Pentacles

Psi-resonant Pentacles were a series of artifacts utilised throughout the chaotic event known as the Horus Heresy by both sides during the conflict.

A class of artefacts recovered from the Vrant Cluster among the troves of the Reclaimants, their Pentacular Crowns or protective armour pieces such as Pentagrammic Sallets and Five-sided Bevors are all painstakingly inscribed with sigils and runes of warding. These markings, through the ill-understood means of their artifice, project an aura around themselves which may slow the passage of time or project waves of force. Least well understood of all, the Pentacles may turn the gaze of the Warp back upon those fated with the gift of warp-sight, blinding them with the turmoil of the aether.

The Thousand Sons Legionaries who discovered these treasures promptly petitioned for them to be destroyed, gaining the support of the Navis Nobilite and the choir of the Astronomican. However, orders sent by the officers of the Sigillite dictated that they were instead to be prohibited from use and remanded to the Throneworld for further study. The barge carrying the entire collection to Terra was lost en-route and the articles within have since been seen on battlefields throughout the galaxy.

History
A vast panoply of the arcane exists within the galaxy, spread far and wide on the worlds and in the fleets of Mankind and the Outsider. Attempting to apply a classification or category based on a single shared property of all of these relics, tangible and intangible, is a nigh-on impossible task, for they are myriad in form and use. The term 'psyarkana' is used in lieu of such a classification, and is considered to be a catch-all term to refer to ill-understandable and ill-definable items or practices, often of ancient or mysterious provenance. Broadly though, psyarkana fall into two groups: techno-arcana and esoterica.

Techno-arcana are usually strange relics and devices based upon what can be loosely understood to function through technological and scientific means, though rarely can these means be reproduced. Such items, be they human or xenos in origin, are recovered from lost civilisations, discovered in the darkest reaches of space or, under the rarest circumstances, created by the artifices of the Imperium. They can be potent archaeotechstamped from those STCs which survived the Age of Strife or alien artifices which predate the evolution of Mankind entirely. Esoterica, however, often refers to intangible rituals, practices and powers as found in ancient manuscripts which are not easily understood. Often these are wielded through psychic or arcane means, and are suggested to interact in some respect with the currents of the Warp, though this is not confirmed to be true in all cases. Whatever the truth behind such arcane articles, all produce effects contrary to our grasp of the order of nature.

Many arcane technologies and strange devices were recovered during the Great Crusade, both relics of Mankind's lost endeavours from the Dark Age of Technology and the product of alien minds and cultures now lost to history. Of these relics few now remain, most were destroyed by the Legiones Astartes as they advanced across the galaxy, deemed too dangerous or profane to remain in human hands. However, some yet survive, either taken as trophies or consigned to the vaults of the Legions or the laboratories of the Mechanicum. In particular, the Iron Hands and their master, Ferrus Manus, proved prolific in their acquisition and subsequent interment of powerful and dangerous relics, a number of which would reemerge after their keeper's death.

During the Horus Heresy, desperation led many to wield psyarkana they little understood or could scarcely control. Those organisations previously forbidden from making use of dangerous techno-arcana, particularly amongst the Mechanicum and Iron Hands Legion, would continue to covet these strange technologies. Those who had once searched for proscribed esoterica, experimenting with their knowledge in secret would go on to openly embrace it. Many would wage their own campaigns contrary to the orders of both the Warmaster and the Emperor to take possession of psyarkana at the height of the Age of Darkness. The use of these psyarkana relics carried with it the risk of terrible consequence, or else irrevocably tainted the user. Regardless, such rituals and devices were sought after by every faction of the Horus Heresy and frequently changed ownership; pried from the lifeless hands of the vanquished.