The Megarachnids are a fearsome and violent Xenos race, resembling giant spiders and winged insects.
Biology and History
The Megarachnids possessed long sword-like claws which appeared to be made from an organic metallic substance, and lived and worked in large swarms. Their bodies were heavily augmented through a technological or biological process that, according to Captain Saul Tarvitz, made it impossible to discern where their bodies ended and their weapons began[Needs Citation].
In the distant past, they fought a terrible war against the Interex but were ultimately defeated. Rather than exterminate their foes, the benevolent Interex exiled the Megarachnids to the planet Urisarach and removed all means of interstellar travel from them.
During the Great Crusade, the 140th Expeditionary Fleet discovered Urisarach, and, ignoring the Interex warning beacons, descended to the surface to pacify the Megarachnids, naming the planet One-Forty-Twenty in the name of the Imperium. Then all contact with the 140th ceased, save for a lone distress call.
The 63rd Expeditionary Fleet answered the call some time later, and took heavy losses during attacks from the Megarachnid warriors once they reached the surface. The planet was nicknamed Murder, as during the distress call Blood Angels Captain Khitas Frome said "This. World. Is. Murder".1x