Quote Originally Posted by Biffoniacus_Furiou View Post
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.
I asked because I wanted to know if there were any indications on how shape-changing magic interacts. If you use a polymorph effect to turn into a True Beholder, can you take the prestige class? If a "natural" True Beholder polymorphs into something else, does it no longer qualify for the class? What I'm picking up is that it's one of those things that was never addressed. Shape-changing stuff gets a lot of that. If an orc druid wildshapes into a bear, does the party ranger's Favored Enemy (orcs) still work? If they want to use Knowledge Devotion, what Knowledge skill would they roll?