In the tabletop miniature wargame Battlefleet Gothic, the Demiurg are an alien race of squat semi-humanoids, who share many traits with the typical fantasy dwarf stereotype: they are avid miners, expert traders, and, in some ways, further technologically advanced than humans. They also bear a particular hatred for goblinoids (Orks in the Warhammer 40,000 universe, of which Battlefleet Gothic is a part).
The Demiurg originate on the far Eastern Fringe of the Galaxy, and are less often found further within the Galaxy. They are an uncommon sight, being almost purely space-borne in their massive and majestic Stronghold class vessels. There is little background available on the Demiurg, leaving their origins, intentions and any possible threat or opportunity they pose to the other races in the Galaxy unknown. The Demiurg are known to be organised into "Brotherhoods", though any further information on, for instance, the numbers, political structure, economic and military weight of a Brotherhood is currently unknown, beyond the rumour that one Brotherhood is typically present upon a Bastion class ship and two to three on a Stronghold class.
The Demiurg are known to have an 'allied' relationship with the Tau, being noted as economic relations of the Tau Empire, and were initially introduced to the Tau via their mutual relations with the Kroot. The Tau acquired their knowledge of ion cannon technology from the Demiurg; this technology is now heavily used by the Tau in their armies and fleets. Two Brotherhoods of Demiurg, the Srry'Tok and Thurm, are known to have joined the Tau Empire.