Teyam Ishtori

Demiliches are formed when a lich, through carelessness or by accident, loses its phylactery. As years pass, the lich's body crumbles to dust, leaving only the skull as the seat of its necromantic power. The lich enters a sort of torpor, its mind left wandering the planes in search of ever greater mysteries. The lich gradually loses the ability to cast spells and its magic items slowly subsume into its new form. Void energy concentrates around the skull, causing some of its bones and teeth to petrify with power and turn into blight crystals. The resulting lich skull, embedded with arcane gemstones and suffused with palpably powerful magic, forms a creature called a demilich.

Despite its near-constant state of inactivity, a demilich grows restless from time to time, especially when living creatures draw near. Only then does the demilich's hunger for life stir once more, causing it to lash out with terrifying bursts of power in attempts to consume vital energy. Unlike an ordinary lich, should the demilich's skull be destroyed, its bond to the world is permanently severed, although some theorize that even then it is not truly slain. Rather, some think that once the demilich is destroyed, its foul and tormented mind is finally free to wander the planes and find new ways to enact its will. For the short-lived common folk of the Material Plane, this is good enough, though eons later a demilich may reappear in the region it once inhabited with a new—and even more insidious—agenda.

To gain more time to complete their goals, some desperate spellcasters pursue immortality by embracing undeath. After long years of research and the creation of a special container called a phylactery, a spellcaster takes the final step by imbibing a deadly concoction or casting dreadful incantations that transform them into a lich. While most undertake this drastic plan to continue their work or fulfill some long-term plan, others become liches because they fear death or to fulfill some malevolent purpose, such as long-sworn revenge. Regardless, the result is permanent and carries with it the potential to alter history—both that of those who transform themselves and of the countless mortals that will inevitably suffer as a result of a lich's new power.

After its metamorphosis, a lich often finds some quiet place to dwell, typically protected by a variety of guardians and traps, for two primary purposes. First, a lich requires solitude in order to plan its elaborate schemes, and second, few mortals (if any) deign to interact with these legendarily corrupt necromancers. One reason begets the other, as the self-imposed isolation of a lich often drives the lich insane, further solidifying its separation from civilization. The longer a lich lives, the more meticulous a planner it becomes, secreting itself within a labyrinth of deadly puzzles, misdirection, and monsters. A lich's servants and guardians are absolutely loyal, either due to their nature (such as constructs or other undead) or as a result of compulsion using powerful magic. Many liches go mad, in time, and the nature of a lich's lair is a good indicator of the undead's current mental state.

For all the protections it arrays around itself, a lich will go to greater lengths to guard its phylactery, as it knows that the destruction of this magical container spells doom for the lich. A lich is notoriously difficult to bargain with, though the threat of damaging its phylactery is a sure way to gain the upper hand in such a negotiation.