A lich is a powerful undead sorcerer who possesses tremendous magical power. During his mortal life as the warchief of the orcish Horde of Draenor, Ner'zhul commanded a number of orcish warlocks, shamans, and even some of Gul'dan's death knights. When these wicked sorcerers were captured by Kil'jaeden and the Burning Legion after the destruction of Draenor, they were transformed into twisted aberrations of their former selves. Ner'zhul became the Lich King at this time. The sorcerers' new, undead bodies, though immortal, were bound to the iron will of Ner'zhul. Since the liches showed unswerving loyalty to their master, Ner'zhul granted them control over the furious elements of the cold north. Now, the liches wield frost magic along with their own considerable necromantic spells. Other liches are former humans and important members of the Cult of the Damned (Kel'Thuzad is one such example).
Service to the Scourge
Liches are among the most powerful spellcasters and allies of the undead Scourge, serving their master with evil intent and great power. Often, they command armies as generals, surrogates for the Lich King himself. They are deeply entwined with the cold power of the grave. As a rule, these creatures are power-hungry, devious, and vicious. They utilize their great intellect and dark powers not only to serve the Lich King, but also to defeat each other in subtle political machinations, gaining strength and renown from each opponent's death. A lich resembles a skeleton with a chill blue glow emanating from within its bones. Liches often dress in flowing robes. These creatures are fond of pageantry and deception; they will often dress in the robes of a king or priest and expect their followers to call them by powerful-sounding names. Sometimes, they claim extraordinary powers granted directly from Ner'zhul himself, acting as though Ner'zhul were a god and they were his chosen priests or prophets. Instead of walking on the ground as mortals do, liches float above it on frosty mist. A lich floats from 6 -12 inches above the ground. Liches cannot trigger pressure plates or similar traps, nor do they leave footprints. Most difficult terrain does not inhibit liches, and they can cross calm water and other liquids with this ability. This movement is otherwise similar to normal movement, so liches can still fall down pits, for instance.
Typically, the Lich King elevates only necromancers to lichdom, but rumors speak of the occasional mage, shaman, or Death Knight who also attains this status. Some tales imply that a spellcaster with enough personal and magical strength can willingly turn himself into a lich, but these reports are unsubstantiated. Some powerful necromancers can temporarily transform themselves into a lich.
Following the defeat of the Burning Legion at Mount Hyjal and the weakening of the Lich King's hold over the Scourge, a few liches, such as Ras Splinterspine and Morbent Fell, chose to serve the Burning Legion and sided with the dreadlord Balnazzar during the uprising of Sylvanas Windrunner.
Every lich has a physical amulet, phylactery, that contains its soul. As long as a lich's phylactery remains intact and undamaged, the lich will eventually regenerate its body and return to undeath. It's unclear if the mechanics of phylacteries are common knowledge; if they aren't, then liches thought dead may still return.
The rogue liches walk Kalimdor with no intention of raising an army as when they were under the command of the Legion. Even a single undead draws attention; putting together a large group will surely get the local populace upset. Instead, these liches harbor a single, driving goal; revenge. They seek out those who helped bring about their downfall, first destroying all that they held dear and then bringing ultimate retribution upon the target. 
Human necromancers are the most likely candidates for liches. Chilling mist billows from this skeletal figure. It floats in a cloud of mist, and black robes flow from its evil form. These liches are evil, cunning and loyal to the Lich King. They serve as generals of armies and as advisors to other powerful members of the Scourge. These liches are somewhat inexperienced and probably new to undead existence, but they are filled with power and arrogance. Liches prefer to have hordes of undead minions surrounding them. These lesser undead creatures protect the lich while he casts spells from a distance. Liches have no qualms about fleeing if the situation warrants.
|[??+]||Prime Servant of the Lich King and majordomo of King Arthas and First of the Necromancers||Scourge||Killable||Frost Shadow Unholy Demonic|
|[??+]||Supreme Overseer of the Cult of the Damned||Scourge||Killable||Frost Shadow Unholy|
|Rage Winterchill||Fought for Archimonde at Mount Hyjal||Burning Legion||Dead||Frost Unholy Demonic|
|Ras Splinterspine||Fought against rebel undead during the siege of Lordaeron.||Burning Legion||Dead||Frost Unholy|
|Morbent Fell||Fought the side of Balnazzar during the siege of Lordaeron.||Burning Legion||Dead||Frost Unholy|
|[34+]||Scourge Invasion mob in the Scarlet Monastery, Tirisfal Glades||Scourge||Killable||Frost Shadow|
|[37+]||Rules Razorfen Downs, Barrens||Scourge||Killable||Frost Unholy|
|[62+]||Overseer of the Scholomance, Western Plaguelands||Scourge||Killable||Frost|
|[60+]||Scourge Invasion mob in Stratholme, Eastern Plaguelands||Scourge||Killable||Frost|
|[61+]||Commands Scourge forces in Andorhal, Western Plaguelands||Scourge||Killable||Frost Unholy|
|[69+]||Found in Chapel Yard, Netherstorm||self||Killable||Frost|
|||Found in Talramas, Borean Tundra||Scourge||Killable||Frost|
|||Prisoner of Thassarian in the Wailing Ziggurat, Borean Tundra||Scourge||Alive||Frost|
|[73+]||Found in Wintergarde Mausoleum, Dragonblight||Scourge||Killable||Frost|
|||Commands Scourge in Drak'Tharon Keep, Grizzly Hills||Scourge||Killable||Frost Arcane|
|||Commands Scourge at The Sundered Shard, Sholazar Basin||Scourge||Killable||Frost|
|||Death knight trainer in Acherus, Scarlet Enclave||Knights of the Ebon Blade||Alive||Frost|
|||Forsaken quest giver found at Gunther's Retreat, Tirisfal Glades||Forsaken||Alive||Unknow|
|||Oversees the assembling of constructs in the Fleshwerks, Icecrown||Scourge||Killable||Frost Shadow|
|||Wanders Corp'rethar: The Horror Gate, Icecrown||Scourge||Killable||Frost Shadow|
|Led the Siege of the Sanguine against the Light's Hope Chapel||Scourge||Incorporeal|
Abrakkar the Wretched, Ordin Frostbane, Kali'naj Dethknell, Din Frostfire, Naze the Eternal, Calis Wraithson, Coldreaver, Cho'Nammoth, Kryptikk Soulslayer, Rak Coldskull, Venim Iceblade, Alandil Lieng, Ra'Sal.