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Yithian, Future

The creature resembles a mollusk with an iridescent, vaguely cone-shaped body about ten feet tall and a wide, snail-like foot. Four protrusions sprout from the dorsal side of the body: two claws, a grasping mouth, and a horrific head bristling with sensing tentacles.

Large swarm of Tiny aberrations, lawful neutral

Armor Class 16 (natural armor)

Hit Points 102 (12d10 + 36)

Speed 25 ft., climb 25 ft.

8 (–1) 21 (+5 17 (+3) 23 (+6 17 (+3) 17 (+3)

Saving Throws Dex +9, Int +10, Wis +7, Cha +7

Skills Arcana +10, History +14, Insight +7, Nature +10, Persuasion +7, Yog-Sothothery +11

Damage Resistances bludgeoning, fire, piercing, slashing

Damage Immunities acid

Condition Immunities grappled, paralyzed, petrified, prone, restrained, stunned

Senses blindsight 60 ft., darkvision 60 ft., passive Perception 13

Languages Aklo, Yithian, any 10 other languages, telepathy 100 ft.

Challenge 12 (8,400 XP)

Special Traits

  • Beetle Scout. At any time, the future yithian can send one of its constituent beetles away from its central swarm to observe. This individual has the same statistics as the swarm except it is Tiny, it has 12 hit points, its weapon damage is always the lower value, and it can’t use Multiattack. The yithian’s main swarm and Beetle Scout share the same pool of movement, action, reaction, and bonus action (so if its body has used an action and moved 10 feet, the Beetle Scout has only 15 feet of movement available and can’t use an action this turn).
  • Illumination. As a bonus action, the future yithian can illuminate its space with dim light or extinguish its light.
  • Innate Spellcasting (Psionics). The yithian’s spellcasting ability is Intelligence (spell save DC 18). It can innately cast the following spells, requiring no components:
    • At will: detect thoughts, hold monster, modify memory
    • 1/day: astral projection (self only)
  • Keen Senses. The future yithian has advantage on Wisdom (Perception) checks.
  • Swarm Mind. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a Tiny beetle. Because they are part of a shared consciousness, the swarm can regain hit points or gain temporary hit points. In addition, the swarm can coordinate the efforts of multiple beetles to form rudimentary limbs to manipulate objects (such as its lightning gun) as if it were a single Large creature. When the swarm is reduced to 0 hit points or when the future yithian chooses to disperse itself as an action, 3d12 constituent beetles survive and escape, using the rules for a Beetle Scout. Only one carries the yithian’s consciousness. It can shift between any of these surviving beetles but can’t become a swarm again until it repopulates. Repopulating the swarm takes 30 days and ample food, or less if multiple beetles regroup in safety.


  • Multiattack. The future yithian makes either two lightning gun attacks or four attacks in any combination with its Bites and Toxic Jets.
  • Bites. Melee Weapon Attack: +9 to hit, reach 0 ft., one target in the swarm’s space. Hit: 14 (4d6) piercing damage, or 7 (2d6) piercing damage if the yithian has half of its hit points or fewer. In addition, the target must succeed on a DC 15 Constitution saving throw or take 18 (4d8) poison damage.
  • Lightning Gun (6/day). Ranged Spell Attack: +10 to hit, range 150/600 ft., one target. Hit: 22 (3d10 + 6) lightning damage.
  • Toxic Jets. Ranged Weapon Attack: +9 to hit, range 20/60 ft., one target. Hit: 5 (2d4) acid damage, or 2 (1d4) acid damage if the yithian has half of its hit points or fewer. In addition, the target must succeed on a DC 15 Constitution saving throw or take 18 (4d8) poison damage.
  • Amnesia (Recharge 5–6). The yithian attempts to erase the memories of a creature it can communicate with telepathically. The target must make a DC 18 Intelligence saving throw. On a failure, it loses all memories except those the yithian chooses to leave intact and the yithian can choose to deal 82 (15d10) psychic damage to it. While amnesiac, the target can’t apply its proficiency bonus on ability checks or Intelligence or Wisdom saving throws. A remove curse or greater restoration spell or similar magic cast on the target restores lost memories. If your game uses insanity and dread (see chapter 4), treat this as an insanity. A creature that succeeds on its saving throw takes half as much psychic damage and can’t have its memory erased by Amnesia for 24 hours (although it still takes psychic damage if targeted again during that time).
  • Mind Swap. See past yithian.


Yithians are massive—typically standing over 10 feet tall and weighing 4 or more tons—and very long-lived. An individual yithian can evade death by mind-switching with another creature. If a yithian’s body is killed before it can switch minds, it does indeed die.

The future Yithian beetle race is just as much the great race as the cone-shaped echinoderms of the Mesozoic (at least once they were conquered), but they are rarer, since travel into the distant future is typically rarer than into the past.

Section 15: Copyright Notice

Sandy Petersen’s Cthulhu Mythos, © 2018, Petersen Games; Authors: Sandy Petersen, David N. Ross, James Jacobs, Arthur Petersen, Ian Starcher.