Lich is an archaic English word for a body, especially a dead body. Its use for a type of undead monster was popularized by Dungeons & Dragons. In Dungeons & Dragons, a lich is a skeletal wizard that was once human but became undead.[1]
According to Dungeons & Dragons co-creator Gary Gygax, the lich in Dungeons & Dragons was inspired by the works of Robert E. Howard.[2]
Origin: Europe An undead priest or powerful magician. One of the most powerful undead, it drains the life from those who see them. Because they continue to research after death, they are highly intelligent wizards.
Lich, named Mystic Morgan in Jack Bros., appears starting on the 9th floor of Grim Reaper's Cavern, floor 12 overall. He will periodically disappear before reappearing and attacking the player character with a ranged attack after a split second. Occasionally, Lich can appear behind walls, wherein the attack will still happen, but fizzle once it hits the wall.
Pixie says the following on the floor in which he is first encountered:
Mystic Morgan is here so don't let your guard down! He'll appear suddenly and use his magic powers on you.