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.
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.