|Attention, Scribe of the Lexicanum!
The first Liche Priests originated in the founding of the Mortuary Cult by the Tomb Kings. They were obsessed with finding a way to overcome death and that was the job of the Mortuary Cult. They were commanded by Settra to find a way to make him immortal, never to die. They failed but in the process found ways of extending their lives.  It was not until the reign of Utep that the priests learnt great secrets and didn't die. They are likely to be the same priests who serve the Tomb Kings now and supposedly the fifth dynasty of priests who didn't die.
They were quite safe in Nehekhara for not even the king could execute them as he required them to protect his body and lengthen his life as much as possible. This way the cult became a very powerful force behind the throne. They also have the duty of tending to the Liche High Priest at the heart of every temple on every necropolis. They must perform various rituals of communication with the dead and repairing parchments of vital information. [1a]
Due to their knowledge they have formidable magical powers and are said to be the ones controlling the king, or at least keeping him from death. Without a priest, an army gradually falls to dust, skeleton warriors collapsing to piles of bones all around. They can also cast spells of devastating power that most other races are completely unaware of.[2a]
The Liche High Priests are the most knowledgeable of all the Liche Priests and are served by many lesser priests within the temple dedicated to the king's Mortuary Cult in very Necropolis. Each priest has a number of tasks to perform, including the Ritual of Awakening, renewing seals on tomb vault portals, remaking inscriptions, deciding the moment of awakening and communicating with the spirit of the Tomb King using oracles.
None can die a natural death and are protected from all enemies for if they fall, so does the rest of the army, including the Kings. Their skin is stretched tight over their bones, likely to rip or drop off at any moment.[1a]
- 5th Edition: Liche Priests use a Scroll of the Dead rather than casting spells. 
- 6th Edition: Nehekharan incantations [1b]
- 8th Edition: Lore of Death, Lore of Light, Lore of Nehekhara. [2a] [2b]
Weapons and Equipment
- 5th Edition: Serpent Staff. May have Magic Items. 
- 6th Edition: Liche High Priest: Hand Weapon. May ride Skeletal Steed. May have Magic Items. May take a Casket of Souls. [1b]
- 6th Edition: Liche Priest: Hand Weapon. May ride Skeletal Steed. May have Magic Items. May take a Casket of Souls. [1c]
- 8th Edition: Hand Weapon. May be mounted on a Skeletal Steed. May take a Magic Items. [2b]
- 1: Warhammer Armies: Tomb Kings (6th Edition)
- 2: Warhammer Armies: Tomb Kings (8th Edition)
- 3: White Dwarf 227 (UK), Tomb Kngs of Khemri Army List, pg. 75
- 4: White Dwarf 238 (UK), Liche Priests, pg. 18-19