This warlock subclass was made in collaboration with the 100+ Full Sail students and alumni that attended my workshop on creating content in pre-existing systems.  I've gone back and rebalanced and reformatted everything for use and publication. Thank you to all who attended and for your aid. May you all find your accolades documented in the Book of Exalted Deeds.

Your patron is a horrific mind flayer whose nature is utterly foreign to the fabric of reality. It might be an Illithid from the Far Realm, the space beyond reality, or it could an Elder Brain that has been lost to time in the Underdark. Its motives are incomprehensible to most, but you understand. You have joined the hive mind. You are its thrall.

Expanded Spell List

The Mind Flayer lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Mind Flayer Expanded Spells

SPELL LEVEL	SPELLS
1st	shield, sleep
2nd	detect thoughts, levitate
3rd	sending, slow
4th	confusion, phantasmal killer
5th	dominate person, modify memory

Tentacles

Starting at 1st level, you can grow tentacles on your face that can be used to make a melee attack. As a bonus action, you grow tentacles around your mouth for 1 minute that you can use to attack with an action. To use the tentacles to attack, use the attack action against a creature. The attack bonus equals your Intelligence modifier + proficiency bonus. On hit, the target takes 2d10 + your Intelligence modifier psychic damage. If the target is Medium or smaller, it is grappled (the escape DC equals your Spell Save DC) and must succeed on an Intelligence saving throw against your Spell Save DC or be stunned until this grapple ends.

Once you use this feature, you cannot use it again until you complete a short rest. 

Mind Blast

Starting at 6th level, you can magically emit psychic energy in a 30-foot cone as an action. Each creature in that area must succeed on an Intelligence saving throw against your Spell Save DC or take 4d8 + your Intelligence modifier 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.

Once you use this feature, you can't use it again until you complete a short rest. 

Psychic Hub

Starting at 10th level, you become aware of the presence of creatures within 5 miles of it that have an Intelligence score of 4 or higher. You know the distance and direction to each creature, as well as each one’s Intelligence score, but can’t sense anything else about it. A creature protected by a mind blank spell, a nondetection spell, or similar magic can’t be perceived in this manner.

Additionally, as an action, you can target one incapacitated creature you can perceive with this feature and establishes a psychic link with that creature until you begin your next long rest. Until the psychic link ends, you can perceive everything the target senses. The target becomes aware that something is linked to its mind once it is no longer incapacitated, and you can terminate the link at any time (no action required). The target can use an action on its turn to attempt to break the psychic link, doing so with a successful Charisma saving throw against your spell save DC. On a successful save, the target takes 3d6 psychic damage. The psychic link also ends if you and the target are more than 5 miles apart, with no consequences to the target. You can form psychic links with a number of creatures equal to your Intelligence modifier (minimum 1).

You regain all uses on a long rest. 

Extract Brain

Starting at 14th level, you can attempt to consume the brain of a target you have grappled by your tentacles. The attack bonus equals your Intelligence modifier + proficiency bonus. On hit, the target takes 10d10 piercing damage. If this damage reduces the target to 0 hit points, you kill the target by extracting and devouring its brain and learn everything it knew.

Once you use this feature, you can't use it again until you've completed a short rest.