During the Fall of the Eldar, the lamentable event that heralded the birth of the Dark Prince Slaanesh, Ulthwé was caught in the pull of the Eye of Terror. Here it has remained for millennia, trapped, where the Immaterium intersects with realspace. It is a breeding ground for Chaos and a gateway into the Warp. Due to this baleful proximity to the Eye, Ulthwé must be on constant high alert in case of attacks by the Forces of Chaos. Constant risk and warfare has hardened this Craftworld's citizens to hardship. Due to the lack of Aspect Warriors on the Craftworld, Ulthwé maintains a standing militia known as the Black Guardians, who are highly skilled and better-trained than the Guardians of other Craftworlds.