Elder Lich

Elder Liches (エルダーリッチ) are powerful immortal undead magic casters, capable of commanding lesser undead with their necromancy and casting highly destructive magic.

Appearance
An old and luxurious robe covered its body of rotting skins and bones. Holding a twisted staff adorned with gems on its end. Beneath its rotting exterior lies a pair of evil eyes brimming with intelligence. Its aura of negative energy covers its body like a thin fog, giving off a menacing atmosphere.

Abilities
Unlike normal undead, a Lich retains its intelligence. Thus, it's capable of complex thought. As a magic caster, the Lich's source of mana comes from negative energy power. However, it is poorly suited for melee battles. A lich is typically around level 30 and is ranked second among undead monsters.

Trivia

 * Apparently there is a ritual in the New World that allows one to become an Elder Lich, but the power to ascend or descend (depending on one's point of of view) to a lich requires the sacrifice of at least the entire population of a city.
 * Khajiit was attempting to turn himself into a Lich by sacrificing the entire population of E-Rantel.
 * Despite the fact that liches are said to be poor melee fighters, Momonga seems to have immense physical strength (though he lacks the skills of a real warrior).
 * It would be challenging to defeat for a platinum-ranked adventurer, and relatively winnable for a mithril-ranked adventurer.