What was the big pillar-shaped Beholder in 3.5?

Question

There was a specific type of Beholder that I used as a shapechange target in 3.5, but I can't remember exactly what it was called, or its specific abilities. What I remember is that it wasn't a floating ball, more like a pillar with eyes sticking out. I believe that it had some kind of ability to freeze things in time, and I believe a dominate person eye ray? It was definitely high-CR, but had few enough hit dice to fall under the limit for shapechange. Possibly the highest-CR Beholder. I believe it was in one of the later books, could be Lords of Madness but also might be in the MM3 or MM4.

What specific monster is this?

Answer 1

I believe you're talking about an "Overseer."

Overseers were among the most dangerous of the beholderkin. Rivaling the power of a hive mother, an overseer resembled nothing more than a large mass of flesh or a tree with mouths on its trunk and eyes on its branches.

Quote from here: https://forgottenrealms.fandom.com/wiki/Overseer

You are correct that it appears in Lords of Madness: The Book of Aberrations, specifically on page 139.

They are CR 15 and yes, among its 13 eye rays is included "Dominate Person."

They also appear in...

• "I, Tyrant" an AD&D 2nd edition supplement
• Appendix 1 to the Spelljammer Monstrous Companion, also a 2nd edition supplement

Contrary to your guess, though, an Overseer is not the highest CR Beholder--that title goes to the Hive Mother at CR 16. For your Hit Dice comparison, an Overseer has 14 hit dice, which makes it accessible at Caster level 14 (assuming access to Shapechange), as opposed to the Hive Mother's 20 hit dice. Still accessible via Shapechange, but requiring Caster level 20.

Answer 2

Probably the Overseer

It originated in 2E, where it was listed as a beholder abomination, and arguably for good reason.

^{(Lords of Madness, pg. 139)}

You will find our freaky fleshy friend in Lords of Madness.