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A neothelid, w is a type of monster that appears in EvilHack. The neothelid is a slithy, strong, and carnivorous animal that is the result of a mind flayer larva undergoing neotony and becoming a gigantic worm-like creature. Neothelids will grudge any monster that is not mindless, as they need brain matter to survive; mind flayers will attack neothelids on sight, as they view them as abominations.

A neothelid has an acid breath attack, four tentacle attacks (three of which can drain intelligence), and an engulfing attack that can digest targets. Neothelids possess acid resistance and psychic resistance.

A neothelid's corpse is acidic to eat.


Neothelids are not randomly generated, and normally-created neolithids are always hostile. They are not a valid form for polymorph.

There is a 110 chance of a neothelid being generated within a mind flayer nursery - the nursery on the middle floor of the Wizard's Tower has a 12 chance of generating one on the middle square.


Neothelids are one of the most dangerous monsters present in EvilHack: They move as fast as an unhasted, unburdened player, deal high physical damage, and can drain as much intelligence as a mind flayer in a single turn. Furthermore, their high level and gigantic size means they will be incredibly tanky. Luckily, due to their rarity, the player often has time to prepare before facing one.

By the time they are likely to be encountered, the player will likely have reflection or acid resistance of some kind, making the breath a light nuisance - the main danger a neothelid presents is its melee tentacle attacks. Intelligence can be protected by wearing a ring of sustain ability, but amnesia will still cause loss of skills and spells, making continuing the fight potentially difficult. Note that neothelids cannot use their tentacle attacks while digesting the player; it may be worth removing any rings of slow digestion to be intentionally swallowed.

Player illithids and draugr are immune to the intelligence-draining effects of the tentacle attacks, as are monster mind flayers. A viable strategy for other characters is to polyself into a variety of mind flayer (minus illithids and alhoons, which are not valid forms) or wear an oilskin cloth helm to prevent intelligence drain.

Ranged attacks are generally effective against neothelids, and perhaps the safest option: A sufficiently large stack of missile weapons or attack wands can work well, as can powerful attack spells. Boulder forts work well for characters with acid resistance to keep neothelids out of melee range, as does simple kiting with a source of speed; centaurs can additionally use their jumping abilities to maneuver around them. The neolithid's magic saving throw of 60 makes it difficult but possible to polymorph one or put it to sleep.


Neothelids originate in Dungeons & Dragons, where they are the result of an illithid larva failing to undergo "ceremorphosis". Illithid larvae are kept within a pool of cerebral fluid in the center of an illithid dwelling, which is also host to an "elder brain" - larvae that survive 10 years of development are then inserted into the brain of a sapient creature selected to be its host, and the elder brain typically consumes those that fail to undergo ceremorphosis. In a pool without an elder brain, the larva are forced to engage in cannibalism in order to survive: any larva that manages to live through the resulting chaos grows to the size of a dog and flees, feasting on rats and other vermin as it grows in size; this larva eventually makes its way to preexisting tunnel systems, typically purple worm tunnels, in order to travel.

Lone larva that survive this far finally become neothelids upon digesting a sentient mind, which causes a similar reaction to that of a larva undergoing actual ceremorphosis, and grants the neothelid self-awareness and psionic powers. These newly-empowered worm-like beasts then constantly hunt for new brains, dissolving their victims' bodies with acid breath and devouring the untouched brains. Neolithids are loathed by illithids, who see them as abominations, and creating one deliberately is seen as a taboo.

Encyclopedia entry

Neothelids are extremely rare creatures, so called as they were
illithid larvae who had undergone neoteny. They typically
appeared once a mind flayer society was destroyed and the larva
nursery left unsupervised. The larval illithids engaged in
cannibalism until the last survivor became a gargantuan leviathan
loathed by all, especially mind flayers themselves. Neothelids
are slime-covered worms with a quadri-tentacled mouth that resembled
gigantic versions of illithid larvae. They were often mistaken for
purple worms due to their purple skin, and massive larval body