Yithian

The yithian has Advantage on saving throws against spells and other magical effects.

The yithian's thoughts can't be read by any means, and other creatures can communicate with it telepathically only if it allows them.

The yithian casts Clairvoyance, Modify Memory, Phantasmal Killer, or Transport via Plants, requiring no spell components and using Intelligence as the spellcasting ability (spell save DC 18).

2/day: Clairvoyance, Modify Memory, Phantasmal Killer

The yithian makes three Pincer attacks. It can replace one attack with a use of Sup.

Melee Attack Roll: +9, reach 10 ft. Hit: 18 (4d6 + 4) Piercing damage and the creature has the Grappled condition (escape DC 14).

Intelligence Saving Throw: DC 18, one creature within 10 feet that has the Grappled, Incapacitated, or Restrained condition. Failure: 15 (3d6 + 5) Psychic damage. The target's Hit Points maximum decreases by an amount equal to the damage taken, and the yithian regains Hit Points equal to that amount.

Intelligence Saving Throw: DC 18, one Humanoid the yithian can see within 5 feet. Failure: The target is possessed by the yithian; the yithian disappears, and the target has the Incapacitated condition and loses control of its body. The yithian now controls the body; the target has no awareness of the yithian's actions. The yithian can't be targeted by any attack, spell, or other effect. The yithian's game statistics are the same, except it uses the possessed target's Speed and Strength, Dexterity, and Constitution modifiers. It knows everything the target knew.

The possession lasts until the body drops to 0 Hit Points or the yithian leaves as a Bonus Action. When the possession ends, the yithian returns to its body, which appears within 5 feet of the target. The target is Stunned for 1 minute by alien memories, and it is immune to this yithian's Mind Swap for 24 hours. Success: The target is immune to Mind Swap for 24 hours.