Watchers in the Dark - History: The nature of the creature under the robes of a Watcher in the Dark is unknown to even the battle-brothers of the Dark Angels. Perhaps the Watchers are simply vat-grown servitor-constructs of an unusual size and form. Perhaps they are some manner of hitherto unknown xenos creature who were native to the Dark Angels' lost homeworld of Caliban. Perhaps they are something more sinister, a corporeal manifestation of the Unforgiven's collective guilt.During the Great Crusade era, a young Knight of The Order by the name of Zahariel, who would later go on to become a Librarian of the Dark Angels Legion, first encountered these mysterious creatures while undertaking a Beast Quest. He recognised these entities as the Watchers in the Dark, creatures who had existed in the ancient legends of Caliban for as long as anyone could remember, living in the darkest regions of the wild hinterlands of Caliban's vast forests.These humanoid entities warned the young knight to cease in the pursuit of his goals. Undeterred, Zahariel continued to undertake his quest. The Watchers in the Dark appeared to oppose Chaos and the powers of the Warp and seemed, on some level, to be attempting to limit or contain the power of Caliban's Warp-tainted Great Beasts.According to the sentient artefact known as the Ouroboros that was discovered on Caliban during the Horus Heresy, the Watchers at some point had become its "jailer."It is said that the Watchers in the Dark are the heralds of troubled times ahead. They appeared before Lion El'Jonson's discovery by the Emperor on  Caliban and just before the eventual betrayal of the Dark Angels Legion by the Dark Angels left behind on Caliban by the Ist Legion who became the Fallen Angels. As conflict erupted during the Horus Heresy between the Fallen Angels garrisoning Caliban, the Watchers in the Dark sided with the Lord Cypher rather than Zahariel and Merir Astelan.During the Fall of Caliban, the great conflagration between the Arch-heretic Luther and Primarch Lion El'Jonson that caused the destruction of the Dark Angels' homeworld, the Watchers in the Dark carried away the mortally-wounded primarch, as the Fallen were swept up in a great vortex and cast into the Warp and scattered throughout time and space.Since that time, the Watchers in the Dark now haunt the lower levels of The Rock. These silent figures have been seen bearing the Dark Angels battle-brothers' weapons into combat and seem near-immune to all acts of violence or use of psychic powers. Any battle-brother of the Dark Angels or the other Unforgiven Chapters who gains the honour of being accompanied by one of these strange beings is incredibly fortunate and is clearly destined for great things.Deep within the bowels of The Rock, known only to the Watchers in the Dark and the Emperor Himself, lies the final and greatest secret of the Dark Angels. Hidden inside a secluded chamber at the heart of what was once the planet of Caliban, unreachable by all save the cryptic Watchers in the Dark, the mighty primarch Lion El'Jonson lay slumbering in a coma, his wounds long-healed, waiting for the time when he will be needed once again, when the clarion call of battle sounds for the final time to defend the Imperium of Man against its enemies.That time came in the Era Indomitus, when the Lion awoke from his millennia-long slumber and was guided by the Watchers in the Dark to travel through the Warp into the Imperium Nihilus where he sought to protect the Imperial worlds trapped behind the Great Rift from the incursions of the forces of Chaos and xenos.