The Lich is a Pureblood Heartless that is featured as a boss in Kingdom Hearts III. According to Young Xehanort, the Lich is not like the other Heartless, and exists to usher hearts into the depths of darkness.
It is based on a sorcerer with mournful yellow eyes, a mostly black body with grey, pink and yellow details on the edges of its body, small sharp pink claws on its hands, and a heart shaped hole in the center of its body. It carries a tall staff with a representation of the Heartless symbol on top. There are also three chains trailing underneath the bottom torso.
The Lich first appears in Olympus after Sora returns from The Final World. The Heartless takes captive the hearts of Sora's friends, leading the Keyblade wielder in a chase across the worlds he had visted before. The Lich eventually meets its end in San Fransokyo, the hearts it had captured having been released and returned.
It stays as far away from Sora while it possesses the hearts of his friends. Whenever Sora catches up to it, it sends a barrage of spells and clones itself to avoid being attacked.