Ancient of thought
Ancients of thought are a possible inhabitant of an ancient-nupperibo-hellish seal. They are notable for their painful stings, their ability to pick up and throw boulders, and their extremely dangerous breath attacks.
Melee attack: jellyfish sting
Monsters struck by this attack lose movement points, and may be stun-locked if hit frequently enough.
The player character instead begins screaming. This alerts all monsters on the level of your true position, and prevents talking, spellcasting, and scroll-reading (syllables of power can still be used).
An ancient of thought inhales thoughts and exhales terrible cries.
"Your mind goes numb."
The inhalation affects one non-mindless target within 4 squares of the ancient at random. The player character is never considered to be mindless, even if polymorphed into a mindless form.
The attack deals 1-5 (1d5) intelligence damage. This damage may cause the character to die of brainlessness. Higher-level ancients gain 1 face on the die per 3 levels (e.g., 1d6 damage at 18th level).
Exhalation: terrible cry
"The ancient of thought screams into your mind!"
The exhalation affects one living, non-mindless target within 8 squares of the ancient. The player character will be targeted if in range, otherwise the target is chosen randomly.
Targets with less than 100 current HP are killed outright, targets with more than 100 current HP are instead heavily damaged. If the character is targeted, they may begin panicking.
All non-mindless targets on the level other than the primary target are affected similarly to a mind blast attack, with a telepathy-dependent chance taking moderate damage. This effect will occur even if there was no primary target chosen (which could occur if there were no valid targets in range).
The breath attack is extremely dangerous. If the character is vulnerable to one or both components of the attack, it is wise to use an escape item and come back with sustain ability and/or a dunce cap. A dunce cap also prevents the exhalation from occurring, so it should be preferred for most characters.
dNetHack ancients are very loosely based on D&D Ancient Baatorians. Only two examples of ancient baatorians were actually encountered during the period in which they were introduced: a nupperibo with constitution-draining tentacles (stated to be a metamorphosing, larval baatorian) and a shapeless thing that inhales light/reflectivity and life and exhales darkness. There were also said to be spined creatures frozen deep under the ice in Cania. A later source claimed that Zargon was another ancient baatorian, but Zargon originated over a decade before the later idea of ancient baatorians (and over two decades before the source tying them together) and is obviously unrelated. That said, the ancient of corruption is based on Zargon's abilities.