The Fall of Prospero, also referred to as the Scouring of Prospero, the Burning of Prospero and the Battle of Prospero, was the name given by later Imperial scholars to the sanctioned Imperial military reprisal against the Thousand Sons Legion of Space Marines' homeworld of Prospero at the start of the Horus Heresy in the early 31st Millennium. The action was carried out by the Space Wolves Legion and elements of the Legio Custodes and the Sisters of Silence as a punishment for the Thousand Sons' flagrant violation of the Emperor of Mankind's edicts against the use of psychic powers and sorcery made at the Council of Nikaea.