The Obsidax is a unique Necron weapon currently in the hands of the Necron Overlord Kutlakh the World Killer. Since before the time of the Necrons' revolt against their C'tan masters, this specially-crafted midnight-black Hyperphase Blade has been carried by the greatest war leaders of the Maynarkh Dynasty, and has ended lives without number across the ages. The blade's edge is bathed in a dark, unknown radiation that has proved deadly to all living matter.
- Imperial Armour Volume Twelve - The Fall of Orpheus, pg. 109