Great Yithian

Large aberration (alien, mythic, mythos), lawful neutral

Armor Class 18 (natural armor)
Hit Points 180 (12d10 + 60)
Speed 20 ft., climb 10 ft.

25 (+7) 16 (+3) 20 (+5) 23 (+6) 17 (+3) 17 (+3)

Saving Throws Con +9, Int +10, Wis +7, Cha +7
Skills Animal Handling +10, Arcana +10, Deception +10, History +10, Insight +10, Intimidation +10, Investigation +10, Medicine +10, Nature +10, Performance +10, Persuasion +10, Religion +10, Survival +10
Damage Resistances acid, cold, fire; bludgeoning, piercing, and slashing from nonmagical attacks
Senses blindsight 60 ft., darkvision 60 ft., passive Perception 20
Languages Aklo, Yithian, any 10 other languages, telepathy 100 ft.
Challenge 11 (7,200 XP)

Special Traits

  • Innate Spellcasting (Psionics). The great yithian�s spellcasting ability is Intelligence (spell save DC 18). It can innately cast the following spells, requiring no components:
    • At will: astral projection (self only), detect thoughts, hold monster, modify memory
    • 1/day: foresight
  • Keen Sight. The great yithian has advantage on Wisdom (Perception) checks that rely on sight.
  • Knowledgeable. The great yithian uses its Intelligence modifier on all Intelligence, Wisdom, and Charisma-based skills.
  • Legendary Resistance (2/Day). If the great yithian fails a saving throw, it can choose to succeed instead.
  • Magic Weapons. A yithian�s weapon attacks are magical.
  • Precognitive Anticipation. A great yithian adds its Intelligence modifier on initiative checks and can always act during a surprise round. This bonus does not apply against creatures using mind blank.
  • Severing Snap. When a great yithian scores a critical hit with its pincers, it may choose to sever one of the target�s limbs in lieu of dealing extra hit point damage. This deals 1d4 points of Strength, Dexterity, and Constitution damage, and 7 (2d6) necrotic damage, and the target may not perform actions requiring that limb. A creature missing an arm cannot use items requiring two hands and has a 50% chance of spell failure when casting spells with somatic components. A creature missing a leg is considered restrained; these penalties stack if the creature also becomes entangled. Ability damage can be healed in the normal fashion, but restoring the severed limb requires a magic like a regenerate spell.
  • Suction. A great yithian can establish or release powerful suction against any horizontal or vertical surface as a swift action. While using suction, its speed is halved but it is immune to the prone condition as well as any effect that would move it against its will. If such an effect also deals damage, that damage is halved while the great yithian is using suction.
  • Temporal Projection. A great yithian can propel its consciousness forward or backward in time. It can use foresight once per day. If it is touching a willing or helpless creature, it can project itself into that person�s past or future self. Projecting itself into the future allows it to obtain visions of the future as if using divination. Projecting itself into the past enables it to seek out the answer to specific questions about that creature�s past, as if interrogating a corpse using speak with dead.


  • Multiattack. The great yithian makes either two pincer attacks or two electric gun attacks.
  • Deadly Pincer. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 23 (3d8 + 10) bludgeoning damage. If the great yithian scores a critical hit, it rolls damage dice three times, instead of twice.
  • Electric Gun (6/day). Ranged Spell Attack: +10 to hit, range 150/600 ft., one target. Hit: 22 (3d10 + 6) lightning damage.
  • Amnesia (1/Day). The great 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 against this effect 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. The great yithian attempts to exchange minds with a creature it can communicate with telepathically. The target must make a DC 18 Charisma saving throw or be possessed by the yithian. On a failed save, the yithian�s soul moves into the target�s body and the target�s soul moves into the yithian�s body. On a successful save, the target is unaffected and becomes immune to that yithian�s Mind Swap for 24 hours. Once the yithian swaps minds with a creature, it takes complete control of that creature�s body. The yithian�s game statistics are replaced by the target�s, though the great yithian retains its alignment and its Intelligence, Wisdom, and Charisma scores. The yithian keeps its Innate Spellcasting trait and its Amnesia and Mind Swap. The yithian can�t use the target�s class features. Meanwhile, the target gains the yithian�s statistics except for alignment and Intelligence, Wisdom, and Charisma scores. The target retains the use of class features compatible with the yithian�s physical form but can�t use the yithian�s Innate Spellcasting trait, Amnesia, or Mind Swap. The target�s ability to use the yithian�s equipment might be limited (for example, trying to wield the large sized lightning gun built for pincers would be challenging for a non-yithian). While the yithian controls another creature�s body, it can use its action to reverse the effect at any range, instantly returning both minds to the proper bodies. If the yithian wishes, it can use its Amnesia action on the creature as a bonus action immediately after reversing the swap. If a possessed body dies, its possessing mind dies with it and the other body permanently retains its possessing mind. Casting dispel magic (treat this as a 6th-level spell) or remove curse on either creature with a swapped mind causes each of the two swapped minds to return to its previous body unless either body is dead. Reviving a body that died while possessed by a swapped mind causes that original mind to return to the revived body, which kills the body left mindless.

Legendary Actions

The great yithian can take 2 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature�s turn. The yithian regains spent legendary actions at the start of its turn.

  • Pincer. The great yithian makes one pincer attack.
  • Auto-Lightning. The great yithian uses its electric gun.
  • Surgical Pincers (Costs 2 Actions). The great yithian makes a pincer attack against one creature within 10 feet of it. The target must succeed on a DC 18 Constitution saving throw or be poisoned for 1 minute. While poisoned in this way, the creature can�t maintain concentration on a spell or any other effect that requires concentration. The poisoned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.


These alien creatures resemble mollusks with an iridescent, vaguely cone-shaped body about ten feet tall and a wide, snaillike foot. Four protrusions sprout from the dorsal side of the body: two claws, a grasping mouth, and a horrific head bristling with sensing tentacles. Untold eons ago, the yithians inhabited a dying world. To escape their doomed planet, they cast their minds through time and space, eventually coming to rest in the strange, alien bodies they possess today. While these strange beings now reside in a distant galaxy, the yithians make use of their ability to astrally project to explore other planets, eager to find new worlds to explore.

Psychic Explorer. When a yithian arrives upon a new world, it often swaps minds with the creatures it encounters there so as to experience that world as if it were a native. Those who spend time in a yithian�s body rarely tell of the strange times they have experienced, for yithians guard themselves well, and leave those they use in this manner amnesiacs who remember the truth only as fragmentary nightmares. Great yithians are the leaders of these psychic expeditions, seeking out new worlds they might inhabit, probing for hidden cells of their enemies, and coordinating the dream intrusions of their lesser kin.

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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