Amygdala

Legendary Resistance (5/Day). If amygdala fails a saving throw, it can choose to succeed instead.

Standing Leap. The amygdala's long jump is up to 40 ft. and it's high jump is up to 60 ft. with or without a running start.

Great One. The amygdala's natural weapons are considered magical and it has advantage on saving throws against magic.

Psionic Veil. The amygdala is invisible to all creatures. This cannot be dispelled, circumvented, or suppressed by any conventional means or magic. Creature's that can't be charmed, are immune to psychic damage, or suffer from a form of madness are immune to this effect.

Spider Climb. The amygdala can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Unknowable. The amygdala can't be targeted by divination magic, perceived through magical scrying sensors, or detected by abilities that would sense aberrations.

Multiattack. The amygdala can use its Maddening Presence. It then takes three slam attacks using it's tentacle attack in place of one of these attacks or an eldritch smash.

Slam. Melee Weapon Attack: +12 to hit, reach 15 ft., # target. Hit: # (2d8 + 6) bludgeoning damage. If the target is a large or smaller creature, it is grappled (escape DC 20). The amygdala has six arms, each of which can grapple one creature.

Tentacles. One creature grappled by the amygdala must make a DC 19 Wisdom saving throw. On a failed save, it takes 36 (8d8) psychic damage and gains a randomly acquired short term madness that only lasts 1 minute or until the creature succeeds their saving throw at the end of their turn. On a successful save the creature only takes half damage. The Amygdala will then drop the target creature whether they failed their saving throw or not.

Eldritch Smash. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 6) bludgeoning damage plus 18 (4d8) psychic damage.

Eye Laser (Recharges 5-6). Amygdala fires a ray of eldritch energy in a 60 ft. long and 10 ft. wide line. Each creature in that area must make a DC 19 Dexterity saving throw, taking 54 (12d8) force damage on a fail and half as much on a success.

Maddening Presence. Each creature of the amygdala's choice that is within 120 feet of it and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened 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, and taking 7 (2d6) psychic damage on a failure. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

The Amygdala can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The Amygdala regains spent legendary actions at the start of its turn.

Slam. The amygdala can take one slam attack.
Move. The amygdala moves up to half its movement speed.
Maddening Presence. The amygdala uses its maddening presence.
Amygdala Leap. (Costs 2 actions). The amygdala leaps into the air and lands in a space within 40 ft of it. Each creature within 5 ft of it when it lands must make a DC 20 Dexterity saving throw. On a failure a creature takes 15 (2d8 + 6) bludgeoning damage and is knocked prone. On a successful save a creature takes half as much damage and is not knocked prone.
Acidic Discharge (Costs 3 actions). The amygdala violently shakes its head, spreading acid in a 20 ft. cube originating from it. Each creature in that area must make a DC 17 Dexterity saving throw, taking 36 (8d8) acid damage and half as much on a successful save. The zone lasts for one round and is considered difficult terrain. A creature takes 18 (4d8) acid damage when it enters this zone for the first time on its turn or if it ends its turn inside the area.