A psionic discipline is a rigid set of mental exercises that allows a Mind Flayer to manifest psionic power. Most creatures master only a few disciplines at a time. Disciplines have many parts

Similarly to a spellcaster's cantrips, psionic talents are the simple and minor psionic effects that a Mind Flayer can use at any time. Some psionic talents grow in power when their user reaches certain levels.

Spellcasting is a powerful tool applied by many across the planes. Psionics, by comparison, are much rarer, and potentially more dangerous. Psionic abilities are not spellcasting, but something wholly different, and the ability is exclusive to several extraplanar beings, such as Mind Flayers. Below is a description of the Mind Flayer's psionic abilities

Now that the Mystic class exists in its Unearthed Arcana form, I wanted to give Mind Flayers their uniquely psionic abilities, and as such, have created this stat block. Warning: these may be more dangerous than default Mind Flayers

The Mind Flayers employ powerful psionics in their efforts to devour brains and control minds. In base 5th edition, psionics were treated as simply a word to tack onto certain monsters who had spells to cast. Considering Mind Flayers are famous for their psionic abilities, it’s strange that their stats in the Monster Manual have them casting the same spells as any wizard or warlock.

Mind Blast (Recharge 5-6). The mind flayer magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 15 Intelligence saving throw or take 22 (4d8 + 4) psychic damage and be stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Extract Brain. Melee Weapon Attack: +7 to hit, reach 5ft., one incapacitated humanoid grappled by the mind flayer. Hit: The target takes 55 (10d10) piercing damage. If this damage reduces the target to 0 hit points, the mind flayer kills the target by extracting and devouring its brain.

Tentacles. Melee Weapon Attack: +7 to hit, reach 5ft., one target. Hit: 15 (2d10 + 4) psychic damage. if the target is Medium of smaller, it is grappled (escape DC 15) and must succeed on a DC 15 Intelligence saving throw or be stunned until this grapple ends.

Innate Psionics. The mind flayer is a 5th level psionic, and its innate psionic ability is intelligence (save DC 15). The mind flayer has 27 psi points and a psi limit of 5, It can innately use the following psionic talents and disciplines, excluding their psychic focus abilities:

Psi Points

You have an internal reservoir of energy that can be devoted to psionic disciplines you know. This energy is represented by psi points. Each psionic discipline describes effects you can create with it by spending a certain number of psi points. A psionic talent requires no psi points. The Mind Flayer has 27 psi points.

Psi Limit

Though you have access to a potent amount of psionic energy, it takes training and practice to channel that energy. There is a limit on the number of psi points you can spend to activate a psionic discipline. For example, the Mind Flayer can spend no more than 5 psi points on a discipline each time it uses it, no matter how many psi points it has.

Psionic Talents

Blind Spot

As an action, you erase your image from the mind of one creature you can see within 120 feet of you; the target must succeed on a Wisdom saving throw, or you are invisible to it until the end of your next turn.

Delusion

As an action, you plant a false belief in the mind of one creature that you can see within 60 feet of you. You can create a sound or an image. Only the target of this talent perceives the sound or image you create.

If you create a sound, its volume can range from a whisper to a scream. It can be your voice, someone else's voice, a creature's roar, a musical instrument, or any other sound you pick. It lasts for 1 minute.

If you create an object, it must fit within a 5- foot cube and can’t move or be reflective. The image can't create any effect that influences a sense other than sight. The image lasts for 1 minute, and it disappears if the creature touches it.

Mind Thrust

As an action, you target one creature you can see within 120 feet of you. The target must succeed on an Intelligence saving throw or take 2d10 psychic damage.

Mystic Charm

As an action, you beguile one humanoid you can see within 120 feet of you. The target must succeed on a Charisma saving throw or be charmed by you until the end of your next turn.

Psionic Disciplines

Intellect Fortress

You forge an indomitable wall of psionic energy around your mind—one that allows you to launch counterattacks against your opponents.

Psychic Backlash (2 psi). As a reaction, you can impose disadvantage on an attack roll against you if you can see the attacker. If the attack still hits you, the attacker takes 2d10 psychic damage.

Psychic Parry (1–7 psi). As a reaction when you make an Intelligence, a Wisdom, or a Charisma saving throw, you gain a +1 bonus to that saving throw for each psi point you spend on this ability. You can use this ability after rolling the die but before suffering the results.

Psychic Redoubt (5 psi; conc., 10 min.). As an action, you create a field of protective psychic energy. Choose any number of creatures within 30 feet of you. Until your concentration ends, each target has resistance to psychic damage and advantage on Intelligence, Wisdom, and Charisma saving throws.

Psychic Assault

You wield your mind like a weapon, unleashing salvos of psionic energy.

Psionic Blast (1–7 psi). As an action, choose one creature you can see within 60 feet of you. The target takes 1d8 psychic damage per psi point spent on this ability.

Ego Whip (3 psi). As an action, choose one creature you can see within 60 feet of you. The target must make an Intelligence saving throw. On a failed save, the creature takes 3d8 psychic damage, and it is filled with self-doubt, leaving it able to use its action on its next turn only to take the Dodge, Disengage, or Hide action. On a successful saving throw, it takes half as much damage.

Id Insinuation (5 psi). As an action, choose one creature you can see within 60 feet of you. The target must make an Intelligence saving throw. On a failed save, the creature takes 5d8 psychic damage, and it goes into a fury, as its id runs rampant. On its next turn, it can use its action only to take the Dodge or Attack action. On a successful save, it takes half as much damage.

By channeling psionic power, you gain the ability to control other creatures by substituting your will for their own.

Exacting Query (2 psi). As an action, you target one creature you can communicate with via telepathy. The target must make an Intelligence saving throw. On a failed save, the target truthfully answers one question you ask it via telepathy. On a successful save, the target is unaffected, and you can’t use this ability on it again until you finish a long rest. A creature is immune to this ability if it is immune to being charmed.

Occluded Mind (2 psi). As an action, you target one creature you can communicate with via telepathy. The target must make an Intelligence saving throw. On a failed save, the target believes one statement of your choice for the next 5 minutes that you communicate to it via telepathy. The statement can be up to ten words long, and it must describe you or a creature or an object the target can see. On a successful save, the target is unaffected, and you can’t use this ability on it again until you finish a long rest. A creature is immune to this ability if it is immune to being charmed.

Broken Will (5 psi). As an action, you target one creature you can communicate with via telepathy. The target must make an Intelligence saving throw. On a failed save, you choose the target’s movement and action on its next turn. On a successful save, the target is unaffected, and you can’t use this ability on it again until you finish a long rest. A creature is immune to this ability if it is immune to being charmed.