Adeptus Custodes

"These men are my bodyguards, their lives forfeit to the guarantee of my physical safety. Of their loyalty to me there shall be no question nor doubt. I, and I alone, shall have the authority to stand in judgement over them. No other commander shall they have in battle nor in service. None shall bar them from me and none shall hamper or stall their mission. So it is decreed!"

—Ancient declaration made by the Emperor of Mankind during the Age of Strife

The Adeptus Custodes, known as the Legio Custodes during the era of the Great Crusade and Horus Heresy, and colloquially as the "Ten Thousand," is the Imperial adepta responsible for protecting the Imperial Palace and the physical body of the Emperor of Mankind, as well as serving as His most important emissaries, His companions, and the keepers of His many secrets. The Custodes is an elite cadre of genetically-engineered transhuman male and female warriors who are even more potent in combat than the Adeptus Astartes. They are to the Space Marines as the Emperor is to His primarchs, and it is rumoured that each was created by the Master of Mankind personally. His might permeates them, burns in their eyes and flows through their veins as surely as their blood. As such, the Adeptus Custodes are widely regarded as the deadliest warriors in the galaxy, Human or otherwise.