Lands of Erdos
Lichdom is a dark path same mages take to attain immortality. By storing their soul into a magical phylactery, their body becomes an ever-rotting corpse suffused with negative energy. Practically immortal and indestructible (since their phylactery re-creates their body should it be destroyed), liches do, however, have to occasionally feed on souls to sustain themselves. Failure to do so reduces them to the form of a demilich, a soul-eating flying skull, merely a shadow of its former self.
Some liches however have discovered means to ascent even beyond that form. One path, is that of Acererak, who discovered means of intentional transformation into a demilich, without losing an ounce of his power or memory. These demiliches are some of the most notorious and dangerous evil entities in the multiverse.
Then there is another path, that of the Izernlich; the Iron Corpse.
The technique was possibly invented by Shadokhan, Acererak’s original teacher (in fact, some believe Acererak developed the intentional demilich transformation because Shadokhan refused to show him how to become an izernlich).
Becoming an izernlich is a long and laborious process. At first it involves the gradual replacement of rotting-flesh body parts with magical machinery. Over time, the compatibility between these mechana and the lich’s rotting corpse attains the desired level and then the final step is taken. The upgrade of the phylactery into a device called an Arcanimus.
The Arcanimus involves the fusion of the lich’s phylactery with the lich’s head and spinal column, all of it encased in a mechanical pod. The arcanimus itself is a miniaturized factory, with the ability to construct a body for the mage, a machine-like humanoid—hence ‘iron corpse.’
An izernlich is not considered an undead and thus can’t be turned with divine power. It is a construct, and its strength and resilience is much greater than that of an ordinary lich. It does not need to consume souls either, instead feeding off magis. Izernliches have displayed the ability to reactively absorb the power of spells, much like a rod of absorption.
Very few izernliches have been observed throughout the multiverse, but it is known that Shadokhan is no longer the only person who has become one such entity of magical destruction.