Beholders are a staple of D&D and one of the popular villains of the genre.

When I used to play D&D a million years ago, one of the pitfalls was always adversaries that had no character, but were a cllection of statistics... So when I design monsters, I always try to make them... memorable. A floating globe of eyes that's smarter than you, can cast spells at will and nullify any magic cast against it by looking at you... Add insanity, a knack for poison gas and a habit of laughing maniacally, and you get "The Laughing Eye Tyrant!"