Bonemold

Hard as bone, tough as leather, and unnaturally flexible. Warlocks of the Brotherhood of the Abyssal painstakingly wrought purple bonemold from corpses deemed unfit to raise as Undead. The arcane processes of Bonemolding used to create this tough substance are a closely kept secret, even among the Warlock Clades.
Bonemold plates are primarily used to create armour for high ranking Liches and Knights of Doom serving within the Legions of Doom. It is also used to create the armoured carapaces of dangerous Undead constructs such as the Bone Worm.