Primordial Mind. Aucantus's weapon attacks are magical. Aucantus can also concentrate on two spells at the same time, but must make two saving throws to maintain concentration on both. Breaking concentration on one spell breaks both.
Unarmored Defense. Aucantus adds her Intelligence modifier to her AC.
Psychic Master. Aucantus's attacks ignore resistance and immunity to psychic damage.
Legendary Resistance (4/day). If Aucantus fails a saving throw, she can choose to succeed instead.
Blink. As a bonus action, Aucantus can teleport up to 30 feet to an unoccupied space she can see.
Break Reality. Aucantus can destroy any barrier using an action. This includes the Forcecage and Prismatic Wall spells.
Magic Resistance. Aucantus has advantage on saving throws against spells and other magical effects.
Head Empty. Aucantus is permanently under the effects of the Mind Blank spell.
Conscious Awakening (Recharges after a Short or Long Rest). If Aucantus would be reduced to 0 hit points, her current hit point total instead resets to 500 hit points, she regains her Psywarp, and she regains any expended uses of Legendary Resistance.
Psychic Spellmaster. Aucantus's innate spellcasting ability is Intelligence (spell save DC 27, +19 to hit with spell attacks). It can innately cast the following spells, requiring no verbal, somatic or material components:
At will: counterspell, detect magic, detect thoughts, dispel magic, cone of cold, raulothim's psychic lance, hypnotic pattern, dimension door, invisibility
3/day each: synaptic static, tether essence, feeblemind, reality break, dark star, maze, forcecage, chain lightning, teleport
1/day each: psychic scream, gate, mass polymorph, prismatic wall, ravenous void, foresight
Multiattack. Aucantus makes one Tentacle Whip attack and uses its Warp once.
Tentacle Whip. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 24 (3d10 + 8) slashing damage. If the target is a Medium or smaller creature, it is grappled (escape DC 24), pulled into an unoccupied space within 10 feet of Aucantus, and must succeed on a DC 24 Intelligence saving throw or be stunned until this grapple ends. Aucantus can’t use the same tentacle whip on another target until this grapple ends. Aucantus has two tentacle whips.
Warp. Aucantus targets one creature she can see within 60 feet of it. The target must succeed on a DC 27 Wisdom saving throw or take 22 (4d6 + 8) psychic damage and become overloaded for 1 minute.
A overloaded creature’s mind is bursting at the seams. The creature has disadvantage on attack rolls, its speed is reduced by half, and if it tries to cast a spell, it must first succeed on a DC 17 Intelligence check or the spell fails and is wasted. The overloaded creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Psywarp(1/form). Aucantus alters the conceptions and thoughts present in any creature's mind around her. Any creatures of her choosing within a 60ft radius of Aucantus must make a DC 27 Wisdom saving throw. On a failure, a creature takes 6d6 psychic damage and must roll twice on the Short-Term Madness table. The madness lasts for one minute. A creature may repeat their saving throw at the end of their turn to remove one Short-Term Madness.
If a creature fails their saving throw against this ability twice before taking a long rest, they must also roll once on the Long-Term Madness table. The Long-Term Madness lasts until the end of their next long rest.
Aucantus 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. Aucantus regains spent legendary actions at the start of her turn.
Attack. Aucantus makes one Warp attack.
Consume Thoughts (Costs 2 Actions). Aucantus targets a creature within 120 feet of her who is concentrating on a spell. The target must succeed on a DC 27 Constitution saving throw or its concentration is broken on the spell, and Aucantus gains 5 temporary hit points per level of that spell.
Mind Meld (Costs 3 Actions). Aucantus connects her psychic energy to another creature within 60 feet of her, taking over their sentience. The target must succeed on a DC 27 Wisdom saving throw or expend one of its spell slots of 3rd level or lower and deal 26 (4d12) force damage to each creature within 30 feet of it. A creature that fails the saving throw but can’t expend a spell slot is instead stunned until the end of its next turn.