In the Plane of Fear: These are rather large versions of Tentacle Terrors. They have the very annoying ability to AE dispell four buff slots.
In Fear Itself: Hits for a max ~7,500.
In Crystal Caverns, Fragment of Fear: Hits for a max ~11,800; does not see invis.
In Heart of Fear: The Threshold: Hits for a max ~13,800; does not see invis.