Demonoid is the first type of self-constructing diagonal spaceship in the B3/S23 rule. A small "0hd Demonoid" was completed by Chris Cain in December 2015, shortly after a much larger 10hd version constructed in November in collaboration with Dave Greene.
The 0hd spaceship displaces itself by 65 cells diagonally every 438,852 generations. As of 2018 it is the only case where a spaceship gun pattern was completed before the actual spaceship -- the first 0hd Demonoid was fired by a gun. Unlike its Gemini predecessor, removal of old construction arms is not done by a separate destruction arm, but rather by "self-destruct circuitry" -- a scattering of still lifes that allow a single glider to cleanly destroy the entire mechanism, as shown at right.