Depleted Necronium is a very dense, utterly mana-dead metal, that is a byproduct of the necronium production process. This metal not only cannot be directly affected by Regular spells or penetrated by insubstantial entities but is very toxic to magical creatures. However, only Depleted Necronium itself is immune to spell effects; encasing an object in it does not protect the object within. Due to how it is produced it is generally limited to TL7 or above.
References[]
- Classic: Technomancer p. 47