beholder (plural beholders)

1. someone who observes or beholds; an observer or spectator
2. a one eyed monster

eye of the beholder

1. The evaluation depending on perception of person who sees and considers.

"Beauty is in the eye of the beholder." — ?
"Whether that was abusive or not, that is in the eye of the beholder." — Randall Vogt

Creative origins

Unlike many other Dungeons & Dragons monsters, the beholder is an original creation for D&D, as it isn't based on a creature from mythology or other fiction. Rob Kuntz's brother Terry thought up the beholder, and Gary Gygax detailed it for publication.[3]

The beholder was later altered by TSR artist Keith Parkinson, who gave it plate-like armoured scales and anthropod-like eyestalks. Jeff Grubb cites Keith Parkinson's artwork as the inspiration for the beholder-kin created for the Spelljammer campaign setting.[4]