Undead Fortitude. If damage reduces the Soul-knife to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the Soul-knife drops to 1 hit point instead.

Psi-Points: 27, Psi-Limit: 5

Psi-casting. The Soul-knife is an 5th-level Mystic. Its discipline ability is Intelligence (spell save DC 15, +7 to hit with spell attacks).

Ethereal Weapon (B) (1 Psi-Point): Makes next act a Dexterity saving throw.

Lethal Strike (B) (1-5 Psi-Points): Add 1d8 psychic  damage per Psi-Point spent on next hit.

Psionic Blast (A) (1-5 Psi-Points): Do 1d6 psychic  damage per Psi-Point spent.

Ego Whip (A) (3 Psi-Points): Do 3d6 psychic  damage and int save half damage on save.

Multiattack: This creature can make two Soul-knife or Mind shot attacks.

Soul-knife Melee Spell Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (1d8+5) psychic damage.

Mind Shot Range Spell Attack: +5 to hit, reach 60 ft., one target. Hit: Int Save (1d4+5) psychic damage.