The Adnector Concillium, also called the Unifiers since their work was intended to unify humanity as never before, were a caste of the ancient Mechanicum of Mars created on the order of the Emperor of Mankind late in the Great Crusade era of the early 31st Millennium. Their sole purpose was to aid the Emperor in the creation of the Imperial Webway extension from the deep vaults of the Imperial Palace on Terra into the broader network of the Webway's labyrinth. As the Emperor sat upon the Golden Throne and used its amplification powers to maintain the psychic wards needed to protect the Adnector Concillium Tech-priests and their bonded labourers from the perils of the Warp, the Unifiers did the actual construction work of creating new tunnels and broad avenues out from Terra into the broader Labyrinth Dimension.
After the Primarch Magnus the Red of the Thousand Sons Legion accidentally breached the Imperial Webway's psychic protections by using a forbidden sorcerous ritual in an attempt to warn the Emperor of Horus Lupercal's betrayal at the start of the Horus Heresy, the daemons of the Warp began to flood into the Imperial Webway. The Adnector Concilium, who had been protected during their work by Mechanicum military forces like Protectors, Battle-Automata, and Thallaxii, began to take heavy casualties. The Emperor deployed His Legio Custodes, the Sisters of Silence and several Titans to throw back the daemonic incursion in what became known as the War Within the Webway.
After the daemonic incursion, the Emperor was forced to remain on the Golden Throne at all times to personally maintain the Imperial Webway's psychic defences and prevent the daemons from breaching the Webway portal into the dungeons of the Imperial Palace. Eventually, despite all their efforts, the Imperial forces proved unable to fully repair and recover the Imperial Webway extension and were forced to retreat back into the Palace. The Adnector Concillium was a part of this retreat. Following the Horus Heresy, after the Terran extension of the Webway was permanently sealed, it is likely that the Unifiers were simply disbanded and reincorporated into the standard formations of the Mechanicum.
- Master of Mankind (Novel) by Aaron Dembski-Bowden, Ch. 2