A Sempiternal Weave is an advanced form of Necron technology used to augment the structural integrity of the Necrodermis bodies of Necron royalty like Necron Overlords, Necron Lords and Necron Destroyer Lords.
A Sempiternal Weave threads a Necron's exoskeleton with filaments of phase-hardened amaranthite and adamantium, vastly increasing the body's structural integrity to a level that rivals that of Astartes Terminator Armour.
- Black Crusade: The Tome of Fate (RPG), pg. 121
- Codex: Necrons (5th Edition), pp. 82, 89-90