Quote Originally Posted by Harrow View Post
I would note that not everyone agrees that losing the prerequisites for a prestige class makes you lose the features of that class, outside of those contained in the couple of books that explicitly state as much, of which I don't recall Lords of Madness being one. You certainly wouldn't be able to take more levels until you qualified again, but losing what you already have isn't guaranteed. Also, is "True beholder" ever defined beyond "not beholderkin"?
It's defined in the same chapter the prestige class is found in, in the section immediately preceding that prestige class. Read the two paragraphs under Beholder Variants on page 41, it briefly discusses the Elder Orb and Hive Mother, then goes on to explain that other beholderkin "...are the subjects of wrath among true beholders..." indicating that all non-beholderkin are considered true beholders.

On page 135 it starts with the beholderkin stats, which includes the Hive Mother but not the Elder Orb. The description of the Elder Orb in Chapter 3 is that it's a standard Beholder that lives longer, typically has higher HD which makes it larger, and doesn't suffer physical ability score penalties for venerable age. That means an Elder Orb is a 'true beholder' but none of the other variants are. There's only one monster in 3.5 that's named Beholder, all others are not true beholders.