Elder Brain

Traits

Creature Sense

The elder brain is aware of the presence of creatures within 5 miles of it that have an Intelligence score of 4 or higher. It knows 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.

Legendary Resistance (3/Day)

If the elder brain fails a saving throw, it can choose to succeed instead.

Magic Resistance

The elder brain has advantage on saving throws against spells and other magical effects.

Telepathic Hub

The elder brain can use its telepathy to initiate and maintain telepathic conversations with up to ten creatures at a time. The elder brain can let those creatures telepathically hear each other while connected in this way.

Actions

Tentacle

Melee Weapon Attack: +7 to hit, reach 30 ft., one target. Hit: 20 (4d8 + 2) bludgeoning damage. If the target is a Huge or smaller creature, it is grappled (escape DC 15) and takes 9 (1d8 + 5) psychic damage at the start of each of its turns until the grapple ends. The elder brain can have up to four targets grappled at a time.

Mind Blast (Recharge 5–6)

The elder brain magically emits psychic energy. Creatures of the elder brain's choice within 60 feet of it must succeed on a DC 18 Intelligence saving throw or take 32 (5d10 + 5) psychic damage and be stunned for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Psychic Link

The elder brain targets one incapacitated creature it can perceive with its Creature Sense trait and establishes a psychic link with that creature. Until the psychic link ends, the elder brain can perceive everything the target senses. The target becomes aware that something is linked to its mind once it is no longer incapacitated, and the elder brain 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 DC 18 Charisma saving throw. On a successful save, the target takes 10 (3d6) psychic damage. The psychic link also ends if the target and the elder brain are more than 5 miles apart, with no consequences to the target. The elder brain can form psychic links with up to ten creatures at a time.

Sense Thoughts

The elder brain targets a creature with which it has a psychic link. The elder brain gains insight into the target's reasoning, its emotional state, and thoughts that loom large in its mind (including things the target worries about, loves, or hates). The elder brain can also make a Charisma (Deception) check with advantage to deceive the target's mind into thinking it believes one idea or feels a particular emotion. The target contests this attempt with a Wisdom (Insight) check. If the elder brain succeeds, the mind believes the deception for 1 hour or until evidence of the lie is presented to the target.

Legendary action uses: 3. The creature can use one option at the end of another creature’s turn and regains spent uses at the start of its turn.

Legendary actions

Tentacle

The elder brain makes a tentacle attack.

Break Concentration

The elder brain targets a creature within 120 feet of it with which it has a psychic link. The elder brain breaks the creature's concentration on a spell it has cast. The creature also takes 1d4 psychic damage per level of the spell.

Psychic Pulse

The elder brain targets a creature within 120 feet of it with which it has a psychic link. Enemies of the elder brain within 10 feet of that creature take 10 (3d6) psychic damage.

Sever Psychic Link

The elder brain targets a creature within 120 feet of it with which it has a psychic link. The elder brain ends the link, causing the creature to have disadvantage on all ability checks, attack rolls, and saving throws until the end of the creature's next turn.

Innate Spellcasting (Psionics)

The elder brain's innate spellcasting ability is Intelligence (spell save DC 18). It can innately cast the following spells, requiring no components:

At will: detect thoughts, levitate

1/day each: dominate monster, plane shift (self only)

Lair actions

When fighting inside its lair, an elder brain can use lair actions. On initiative count 20 (losing initiative ties), an elder brain can take one lair action to cause one of the following effects; the elder brain can't use the same lair action two rounds in a row:

• The elder brain casts wall of force.
• The elder brain targets one friendly creature it can sense within 120 feet of it. The target has a flash of inspiration and gains advantage on one attack roll, ability check, or saving throw it makes before the end of its next turn. If the target doesn't or can't use this benefit in that time, the inspiration is lost.
• The elder brain targets one creature it can sense within 120 feet of it and anchors it by sheer force of will. The target must succeed on a DC 18 Charisma saving throw or be unable to leave its current space. It can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Regional effects

The territory within 5 miles of an elder brain is altered by the creature's psionic presence, which creates one or more of the following effects:

• Creatures within 5 miles of an elder brain feel as if they are being followed, even when they are not.
• The elder brain can overhear any telepathic conversation happening within 5 miles of it. The creature that initiated the telepathic conversation makes a DC 18 Wisdom (Insight) check when telepathic contact is first established. If the check succeeds, the creature is aware that something is eavesdropping on the conversation. The nature of the eavesdropper isn't revealed, and the elder brain can't participate in the telepathic conversation unless it has formed a psychic link with the creature that initiated it.
• Any creature with which the elder brain has formed a psychic link hears faint, incomprehensible whispers in the deepest recesses of its mind. This psychic detritus consists of the elder brain's stray thoughts commingled with those of other creatures to which it is linked.

If the elder brain dies, these effects immediately end.