The Mitu were a race of Xenos that dominated the Coronid Reach region of Segmentum Obscurus during the Age of Strife. This tyrannical empire, known as the Mitu Conglomerate, ruled both Human and other xenos worlds.
The Mitu were pseudo-actinaric psychic beings who are believed to have evolved from common livestock. They were capable of manipulating the Warp thanks to advanced technologies which were biological in nature. They forbid any attempt of space travel by the enslaved worlds of their pocket empire and viciously purged all Psykers they came across. The Mitu were known to periodically cull the population of their slave worlds and demand a tribute of flesh which is believed to have powered their arcane technologies.
During the Great Crusade, the Mitu battled against an invasion by the newly formed Imperium of Man. The conflict was largely fought in space and consisted of brutal close-quarters boarding engagement. Ultimately, the conflict required three Space Marine Legions including the Imperial Fists and hundreds of Solar Auxilia Cohorts. The Mitu were crushed and their worlds subjected to Exterminatus, while the enslaved human planets were liberated and reformed into the Manachean Commonwealth.