Aberrations

Beholders

When you listen to the myths and legends of these creatures, I often hear nothing that would remind me of abberance, but rather themes of narcisism, xenophobia, and self-enrichment, which are simple mortal traits. Beholders are much more dark and twisted, vile insults to the normality of life.
Beholders are aberrations, beings beyond the known bounds of reality, and nothing about them conforms to known lore of nature or the world of Cynthia as a whole. They are grotesque and malformed to mortal eyes -- merely looking at them will make your flesh crawl, often literally. Their surroundings reshape themselves in the gaze of the Beholder, forming into whatever madness is harbored in their imagination. Their mere presence makes the world around them aberrant.
Despite common legends, a beholder does not shoot multicolored beams from their multitude of eyes. This myth has been spread by deceitful adventurers that have likely never experienced a beholder in person. Instead, whatever their eyes focus on, the world twists in unsettling ways. Flesh becomes stone, gravity becomes meaningless, courage evaporates.
Another myth is that beholders woould be considered lawful evil. This is antithetical to the very nature of beholders -- how they alter the world around them, and to their aberrant nature. Change is a beholder's purpose, twisting and recreating the realm as they imagine it to be. Maybe they're curious about breaking the laws of physics and nature, or maybe reshaping their environment ammuses them.
Look not to legends like Xanathar, depicted as a floating disco-ball running a crime syndicate. That is low-hanging fruit for a being that defies mortal comprehension. Beholders are heralds to a reality-churning apocalypse. They are dreamed into being by a slumbering Great Old One and their very existence whispers of an inevitable doom. Some believe that a beholder is the existential threat itself; an ancient deity followed by cults that believe that the world only exists because it is being percieved by that which beholds it from the darkness of the void.
Beholders need not to conform to our depictions of their existence, rather, true witnesses have described these vile creatures as a roiling ball of resculpting flesh with bubbling eyes that open and close, disappear and reappear, like a floating shogoth.