The crypteks are the arcane engineer-priests of the necrons, descended from a caste that once served the necrontyr as court viziers, astrologers, alchemists and tenders of the dead. Across the aeons those priests became something far stranger: masters of technologies so advanced they resemble sorcery, organised into secretive pan-galactic conclaves each devoted to a particular discipline. The Technomancer walks the discipline of preservation and repair, and of all the cryptek orders it is the one a phalanx is most grateful to have at its side.
On the battlefield a Technomancer is a fount of restorative energy. Where its gaze falls, sparking wounds in necrodermis seal themselves, severed limbs realign, and warriors cut down moments before rise once more to resume their advance. The adept commands drifting clouds of nanoscarabs and slaved canoptek constructs, directing them to swarm over the damaged and the destroyed, and can pour raw reanimating power into a wavering line to drag it back from oblivion.
This mastery makes the Technomancer a linchpin of necron warfare, for it turns an already implacable foe into one that seems truly impossible to put down. An enemy may shatter a formation only to watch it knit itself whole again under the Technomancer's cold ministrations, the same corpses standing and firing anew. To fight such a host is to learn that killing a necron and keeping it dead are two entirely different labours.