The Elder Brain

Nightmarish, alien invaders from another time and place, illithid typically live in societies of their own kind, hidden away from the light of the sun. They feed on the brain matter of living creatures, preferably the grey cells of other sapient beings, to sustain themselves and fuel their strange and unnatural powers. Their culture reveres the Elder Brains, ancient, ageless beings they believe represent the collective personalities and identities of their kind, and it is one of these aboreal beings with which you have forged a pact. An undoubtable source of power and knowledge, loyal servants are rewarded with expanded mental prowess and psionic ability, but be wary; the clawing desires of the Elder Brain are undoubtably something to be dubious of, regardless of your intentions. More than any other, the ultimate ends of your patron remain occluded to you--but it is safe to say they aren't good for the long run.

 

Expanded Spell List

The Elder Brain 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.

Elder Brain Expanded Spells

Spell Level	Spells
1st	Command, Dissonant Whispers
2nd	Calm Emotions, Zone of Truth
3rd	Nondetection, Sending
4th	Confusion, Divination
5th	Geas, Modify Memory

Mental Assault

Starting at 1st level, when a creature would make a saving throw against a Divination, Enchantment, or Illusion spell you cast using a Pact Magic slot or your Mystic Arcaneum feature, you may have that creature make an Intelligence saving throw instead of the defaulted option. If the spell allows the creature to make additional saves on subsequent turns, those become Intellignce saving throws as well.

Additionally, if the spell initially required an Intelligence saving throw, they instead make their initial saving throw at Disadvantage. 

Finally, a creature can not benefit from immunity to the Charmed condition against a spell cast in this way.

You may use this feature a number of times equal to your Charisma modifier (minimum of 1). You regain all uses on a Long Reat. 

Psychic Inquisitor

Starting at 6th level, you adopt the thought-piercing powers of the elder brain.

You learn the Detect Thoughts spell. This is a Warock spell for you, and does not count against your spells know.  

When you cast this spell using a Pact Magic slot, it has altered properties, outlined below:

• The duration becomes 1 hour, and no longer requires concentration
• All creatures make saving throws to and ability checks to end or resist your probing at Disadvantage
• The maximum range of detection increases from 30 to 60 feet. At level 11, the range increases to 90 feet. At level 17, the range increases to 120 feet.

Grow the Hive

Starting at 10th level, you can establish small hiveminds—a gift of trust from your domineering patron.

As an action, you may cast Rary's Telepathic Bond without expending a spell slot.

When cast in this way, the duration is increased to a number of hours equal to your Charisma modifier (minimum of 1), and immediately ends if you become Incapatitated.

Additionally, creatures gain the following benefits while they remain linked:

• A creature may behave as if it has proficiency in Intelligence saving throws if any creature it is linked with has proficiency in Intelligence Saving Throws
• A creature may behave as if it has proficiency in Wisdom saving throws if any creature it is linked with has proficiency in Wisdom Saving Throws
• A creature may behave as if it has proficiency in a lanugauge that any creature it is linked with is proficient in

Once you use this feature, you must finish a Long Rest before doing so again.

 

Mind Blast

Starting at 14th level, you are gifted the signature ability of the Ilithid, the mind blast.

As an Action, you can expell a 30 foot cone of forceful psychic energy. Each creature in the cone must succeed an Intelligence saving throw or take psychic damage equal to 5d8 + your Charisma modifier and be Stunned until the end of your next turn. On a success, a creature takes half this damage and isn’t stunned.

Once you use this feature, you can’t use it again until you finish a Short or Long Rest