Large aberration (mythos), chaotic evil

Armor Class 16 (natural armor)
Hit Points 127 (15d10 +45)
Speed 10 ft., fly 40 ft.

20 (+5) 15 (+2) 16 (+3) 19 (+4) 17 (+3) 17 (+3)

Saving Throws Int +7, Wis +6, Cha +6
Skills Arcana +7, Insight +6, Perception +6, Stealth +5
Damage Resistances bludgeoning, piercing and slashing from nonmagical attacks
Condition Immunities charmed, frightened
Senses darkvision 60 ft., passive Perception 16
Languages Common, Abyssal, Deep Speech, Dark Speech, Draconic, telepathy 100 ft.
Challenge 8 (3,900 XP)

Special Traits

  • Brain Collection. The nehthalggu, or brain collector, can store up to ten humanoid brains and use them to enhance its knowledge and power. The destruction of these brains causes the brain collector to lose some of its magical power. Each brain can be attacked (AC 20: 15 hit points). Destroying a single brain deals no damage to the brain collector but causes it to lose special abilities. The number of brains determines its additional special attacks. It may use each of these abilities once per day. These abilities are psionic in nature (treat as spellcasting). Its psionic ability is Intelligence (spell save DC 15, +7 to hit with these attacks). Some options are passive and are active so long as the nehthalgaa has the appropriate number of brains. It may also maintain as many concentration spells as it has brains: 0: No additional special abilities.
    • 1-4: Mind Worm. The neh-thalggu targets a creature it can see. The target creature must make an Intelligence save or have disadvantage on Intelligence saving throws until the neh-thalgaa is dead or loses this trait. The target is also slowed (as the slow spell). The neh-thalggu may use this ability once per day per brain up to four times per day.
    • 5: Whispers of Madness. The neh-thalggu makes a ranged spell attack against a target within 100 feet that it can see; on a hit, the target takes 16 (3d8 +4) psychic damage and must pass an Intelligence save or become slowed (as the spell slow). If already slowed the target is paralyzed
    • 6: Invisibility. As the spell of the same name.
    • 7: Bend Space (passive). The neh-thalggu gains a reaction. If the neh-thalgaa would be hit by an attack, it can teleport up to 15 feet. This does not provoke an opportunity attack.
    • 8: Distortion Blast. All creatures in a 100-foot long line that is 5 feet wide must make an Intelligence save or take 32 (8d6 +4) psychic damage. Aberrations have advantage on this save and only take half damage.
    • 9: Venomous Mind. All creatures within 5 feet of the nehthalggu must make an Intelligence save or take 8 (1d8 +4) psychic damage and become confused (as the spell) until the end of the neh-thalggu�s next turn. The creature then uses its reaction to make a single melee attack against a random adjacent creature.
    • 10: Celerity (passive). The neh-thalggu may make its normal attacks as well as use a psionic ability or attack listed on this table.
  • Cerebral Power (Recharge 6). The neh-thalggu uses the power of its collected brains to supercharge its magic. The brain collector can use this ability as a bonus action to cause the target of one of its spells to make any saving throws against its brain collection trait with disadvantage.
  • Magic Resistance. The brain collector has advantage on saving throws against spells and other magical effects.
  • Strange Knowledge. A neh-thalggu may add its proficiency bonus to all knowledge related ability checks.


  • Multiattack. The neh-thalggu makes three attacks: one with its bite and two with its claws.
  • Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 5) piercing damage, and the target must succeed on a DC 14 Constitution saving throw or be poisoned for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
  • Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage. If the target is a creature, it is grappled (escape DC 15). Until this grapple ends, the target is restrained, and the neh-thalgaa can�t use one of its claw attacks on another target. However, the grappled creature automatically takes 14 (2d6 + 7) bludgeoning damage at the start of the neh-thalggu�s turn. The neh-thalggu has two claws it can use to grapple a target.
  • Collect Brain. Melee Weapon Attack: +8 to hit, reach 5 ft., one incapacitated, stunned or paralyzed humanoid grappled by the brain collector. Hit: The target takes 55 (10d10) slashing damage. If this damage reduces the target to 0 hit points, the brain collector kills the target by extracting and collecting its brain.


Known also as brain collectors, the alien neh-thalggus hail from distant worlds, traveling the gulfs of space on immense living ships that swiftly decay when they land upon a new world, leaving behind a deadly cargo of hungry monsters. Neh-thalggus are crablike nightmare with lamprey-like mouths, twitching eyes on its legs, and several blisters along its back that hold human brains. Some speculate that neh-thalggus encountered in this reality may merely be juveniles of their kind, perhaps exiled from their home worlds by greater kin until they can prove their worth on other worlds.

Brain Collectors. Neh-thalggus are carnivores, but they do not digest humanoid brains they eat�rather, these brains lodge in one of several bulbous blisters on the creature�s back and help to increase its intellect. Their brain collections may be a morbid form of currency in their home realm, or the thoughts in these brains may merely be fuel for a dark apotheosis into an even more sinister mature form.

Mind Masters. Neh-thalggu masters lord it over their lesser kin by applying the drained brainpower of their victims toward mastering psychic magic and mesmerism. They may inhabit elaborate mindscapes as their lairs or may subtly influence the thoughts and senses of creatures they lure into their lair in furtherance of convoluted plots to manipulate the societies around them while they dwell in secret. Some dwell alone or with mind-controlled slaves, while others organize clusters of their own kind to spread their sinister schemes and feed their insatiable alien hunger.

Section 15: Copyright Notice

Mythos Monsters (5E) © 2020, Legendary Games; Authors Michael "solomani" Mifsud, Robert J. Grady, Mark Hart, Jeff Ibach, Alex Riggs, Scott D. Young, Jeff Lee, Matt Kimmel, and Jason Nelson.

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