Fiction:The Firmament/Lich

A lich is a type of intelligent undead who is considered the apex of a necromancer's power over the dark arts. With decades of study and mastery of necromancy, these individuals have willingly transformed into powerful undead beings to achieve great power and immortality. At the culmination of the process of becoming a lich, a necromancer transfers their soul into an object called a phylactery; as long as the phylactery remains intact, the lich cannot die.

Appearance
No two liches are alike; some allow their bodies to continue to decay, resembling fearsome zombies or animated skeletons, while others go out of their way to preserve themselves. As liches are always master wizards, many have the ability to transform themselves into beings that look alive or hide their true, rotten forms away with illusions.

Characteristics
While most sentient creatures find the idea of becoming a lich abhorrent, certain spellcasters see it as a means of achieving immortality in order to continue their work and ambitions without having to worry about the eventual decay of their mind and body. The process itself is a quite difficult and lengthy one, as no two liches achieve their undead state by the same method.

The spellcaster must first research the construction of a phylactery, generally taking the form of a gem, box or other small object, and then discover the means by which to transfer their soul into the receptacle. As no two bodies or souls are the same, each of these processes are unique to the individual; what has worked in the past might kill or drive another person insane, and the process of achieving lichdom generally takes months, years, or even decades of research.

A lich cannot be permanently destroyed while their phylactery exists; while their physical body can be slain, the phylactery will create a new one after a certain period of time. Because of this, liches generally keep their phylacteries well hidden, for their destruction leads to their immediate demise.