The spear is the instrument of Mars in the same way that Jupiter wields the lightning bolt, Neptune the trident, and Saturn the scythe or sickle. A relic or fetish called the spear of Mars was kept in a sacrarium at the Regia, the former residence of the Kings of Rome. The spear was said to move, tremble or vibrate at impending war or other danger to the state, as was reported to occur before the assassination of Julius Caesar. When Mars is pictured as a peace-bringer, his spear is wreathed with laurel or other vegetation, as on the Ara Pacis or a coin of Aemilianus.