Beholder

The beholder is a powerful, flying abomination. It looks like a floating head with a large mouth and a single large eye in front, and ten eyestalks coming out of the top. Each eyestalk shoots a different magical ray. When attacking the beholder will shoot a ray from one of its eyes. Being hit will cause a random harmful potion effect. The beholder can create all the harmful effects in the game, and sometime more than one will be applied at the same time. Fortunately, they are slow moving and can be easily hit with arrows, just be sure you can take cover from its attacks.

Origin

The beholder comes from Dungeons & Dragons and has been in D&D since 1975.

Trivia

In early version of Dungeon Mobs the beholder could permenantly remove enchantments from gears. This was removed from the mod.

The beholder is the inspiration for the Cacodemon from Doom games. As Minecraft ghasts seem a lot like cacodemons it may also indirectly inspired them as well.