Brain Boyz is a name used by the Orks to refer to their ancient creators, who may be the long-lost starspanning xeno species known as the Old Ones. The Old Ones created a warrior race known as the Krork, from which the modern Orks may derive. It is believed that the Brain Boyz engineered the Orks to be their warrior caste alongside the ancestors of the Eldar, using them as essentially humanoid biological weapons to protect them against various other ancient races. In the Old Ones' case, the Krork were created as part of a desperate ploy to defeat their ancient enemies, the Necrons and their C'tan masters, during the galaxy-spanning conflict known in Eldar Mythology as the War in Heaven over 60 million standard years ago.
The Brain Boyz are believed to have encoded various forms of technological and scientific information into the genetic structure of the Orks at a cellular level, as well as provided the Greenskins with their unusual gestalt psychic abilities that grow stronger as the number of Orks in a given locale increases. Therefore, an Ork engineered to be a Mekboy is born with an understanding of the basic principles of physics, along with "Orky know-wots" that allow him to maintain a relatively high level of technology for such a barbaric and uncivilised species. Almost all Orks are born with the knowledge of how to hammer bits of scrap metal together and create and operate basic Ork weapons of war, while the Mekboyz intrinsically understand how to assemble a Killa Kan, or a Battlewagon. Likewise, Ork Painboyz are born with a simple understanding of Orkoid physiology that allows them to tend to the injuries of their fellow Greenskins with very painful and often very unnecessary surgeries.
- Codex: Orks (4th Edition)
- Codex: Necrons (3rd Edition)