Aeiros

Legendary Resistance (5/Day): If the Great Old One fails a saving throw, it can choose to succeed instead.

Regeneration: The Great Old One regains 30 hit points at the start of its turn. If it takes radiant damage, this trait doesn't function at the start of its next turn.

Reality Warp: The Great Old One can alter the fabric of reality within a 1-mile radius. It can create difficult terrain, change the environment (such as turning a forest into a desert), or impose disadvantage on all saving throws against fear or charm effects. These changes last until the Great Old One is defeated or leaves the area.

Cosmic Aura: At the start of each of the Great Old One's turns, creatures within 60 feet of it must make a DC 25 Wisdom saving throw. On a failed save, they are either frightened or charmed (Great Old One's choice) 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.

Multiattack: The Great Old One makes three attacks: one with its Tentacle, one with its Cosmic Grasp, and one with its Mind Blast.

• Tentacle: Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 30 (4d10 + 9) bludgeoning damage. If the target is a creature, it is grappled (escape DC 25). Until this grapple ends, the target is restrained.

• Cosmic Grasp: Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 25 (3d12 + 9) psychic damage. The target must succeed on a DC 25 Intelligence saving throw or be stunned until the end of its next turn.

• Mind Blast (Recharge 5–6): The Great Old One emits a blast of psychic energy in a 120-foot cone. Each creature in that area must make a DC 25 Intelligence saving throw, taking 60 (11d10) psychic damage on a failed save, or half as much damage on a successful one. On a failed save, a creature is also stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the stunned condition on itself on a success.

Warping Shroud

• Description: The Great Old One surrounds itself with a swirling aura of cosmic energy, distorting space around it.
• Effect: The Great Old One gains +2 to its AC and imposes disadvantage on attack rolls against it until the start of its next turn.

Eldritch Whisper

• Description: The Great Old One whispers maddening secrets into the minds of nearby foes.
• Effect: The Great Old One can choose one creature within 30 feet. The target must succeed on a DC 26 Wisdom saving throw or be frightened until the end of its next turn. If the target is already frightened, it takes 20 (4d10) psychic damage.

Reality Flicker

• Description: The Great Old One briefly shifts its form to another plane, creating a momentary confusion.
• Effect: The Great Old One can teleport up to 60 feet to an unoccupied space it can see. After teleporting, it can cause a burst of psychic energy in a 10-foot radius centered on its new location. Each creature in that area must make a DC 26 Intelligence saving throw, taking 20 (4d10) psychic damage on a failed save or half as much damage on a successful one.

Cosmic Reflex (Recharge 5–6)

Reaction: When a creature within 60 feet of the Great Old One makes an attack roll or saving throw, the Great Old One can use its reaction to impose disadvantage on the roll.

• On a failed attack roll: The attack misses, and if the attack was a melee or ranged weapon attack, the attacker must make a DC 26 Constitution saving throw or suffer 10 (3d6) psychic damage as the attack is distorted by cosmic forces.

• On a failed saving throw: The creature takes 30 (6d10) psychic damage, and if it was a saving throw against an effect that would have caused a condition (such as being stunned or frightened), the creature is also stunned or frightened (Great Old One’s choice) until the end of its next turn.

Description: The Great Old One manipulates the cosmic energies around it, distorting reality to disrupt attacks and save attempts. This reaction reflects its ability to influence the very fabric of the universe to protect itself or its plans.

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

• Tentacle Attack: The Great Old One makes one Tentacle attack.
• Cosmic Pulse (Costs 2 Actions): The Great Old One releases a pulse of cosmic energy. Each creature within 30 feet of it must succeed on a DC 25 Constitution saving throw or take 22 (4d10) necrotic damage and be blinded for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the blindness on itself on a success.
• Warp Reality (Costs 3 Actions): The Great Old One distorts reality around a creature it can see within 60 feet. The target must make a DC 25 Wisdom saving throw or be banished to a pocket dimension for 1 minute. The target is incapacitated and can only see an endless void. It reappears in the space it left or the nearest unoccupied space at the end of the duration.

Void Annihilation (Recharge 6)

The Great Old One unleashes a 300-foot-long line of void energy that is 10 feet wide. Each creature and object in the line must make a DC 26 Dexterity saving throw.

On a failed save: The target takes 150 (20d12) force damage plus 70 (20d6) psychic damage. If reduced to 0 hit points, the target is disintegrated, leaving only dust.
On a successful save: The target takes half damage and is not disintegrated.

Void Annihilation bypasses resistances to force and psychic damage and destroys any barriers in its path, leaving a deep trench or scorched path behind.