Avatar of Ilvaash

A Thousand Possibilities. The first Attack Roll or Ability Check the avatar makes on each of its turns against any target gains a +9 bonus.

Creature Sense. The avatar is aware of creatures within 100 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.

Cull the Weak (Mythic Only). When the avatar reduces a creature down to fewer hit points than double the number of the avatar's mutations, it dies and all creatures within 10 ft. of the slain creature take Psychic damage equal to its highest ability score + 10.

God-Brain's Descendant (Mythic;Recharges after a Short or Long Rest).  When the avatar is reduced to 0 hit points, it does not die or fall unconscious. Instead, it recovers 325 hit points and gains 175 temporary hit points, recharges its Mind-Warping Blast, regains all expended uses of its Legendary Resistance, and gains access to the “Mythic Actions” section for 1 hour. Additionally, when this trait activates, it immediately becomes the avatar's turn and it fuses the astral plane with the landscape around it. For 1 hour, the area in a 300-foot radius around the avatar became a distorted. The area becomes part of the Astral plane. All terrain, objects, and creatures remain the same, but all creatures are subject to the conditions of the Astral plane as described in chapter 2 of the Dungeon Master's Guide. In the avatar leaves the area, the effect is ended early.

If a creature(s) leaves the radius, they must make a DC 27 Charisma saving throw. On a successful save, the creature decides whether they end up in the Astral plane or the Material plane, either way appearing in the location they would have if they normally walked out of the area in the single plane. On a failed save, the location is determined randomly.

At the end of the duration or when the avatar dies (whichever comes first), all creatures in the area make a DC 27 Charisma saving throw. On a failed save, the creature is teleported to the avatar's choice of the material plane of the Astral plane. On a successful save, the creature decides. Reward a party an additional 300,000 XP (455,000 total XP) for defeating the Avatar of Ilvaash after its God Brain's Descendant trait activates.

Incorporeal Movement. The avatar can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

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

Magic Resistance. The avatar has advantage on saving throws against spells and other magical effects.

Omnipotent. The avatar adds its Intelligence modifier to all psychic and force damage rolls it makes (included in attacks) and is unaffected by spells of the Illusion, Conjuration, and Enchantment schools.

Psionic Concentration. When the avatar casts a spell that requires concentration, it can instead choose a creature under the effects of its Telepathic Hub feature. That creature concentrates on the spell instead of the avatar, as if that creature had cast the spell. That creature chooses whether or not to end concentration, must make concentration saves when it takes damage, and cannot concentrate on any other spells. Likewise, the avatar does not need to make concentration saves, nor is it repented from casting other spells that require concentration.

Regeneration. The avatar regains 30 hit points at the start of its turn. If the avatar takes radiant damage, this trait doesn’t function at the start of its next turn. The avatar dies only if it starts its turn with 0 hit points and doesn’t regenerate.

Telepathic Eavesdropping. The avatar can overhear any telepathic conversation within 100 miles of it. The creature that initiated the telepathic conversation makes a DC 27 Wisdom saving throw when telepathic contact is first established. If the save is successful, the creature is aware that something is eavesdropping. The nature of the eavesdropper isn’t revealed.

Telepathic Hub. The avatar can use its telepathy to initiate and maintain telepathic conversations with up to two hundred creatures at a time. The avatar can let those creatures telepathically hear each other while connected in this way.

Unknowable Terror. When an attack misses the avatar, the creature that made that attack takes psychic damage equal to its attack modifier + 10.

Multiattack. The avatar makes three attacks with any combination of its Dissonant Claw or Tentacle Whip and casts one spell. The avatar can replace its Tentacle Whip attack with Extract Brain if it has a creature grappled, or two attacks for Shield of Thralls.

Dissonant Claw. Melee Weapon Attack: +19 to hit, reach 10 ft. or range 120 ft., one creature. Hit: 29 (3d12 + 10) psychic damage. If the target is a creature concentrating on a spell, its concentration is broken, it takes an additional 13 (1d6 + 10) force damage times the level of the ended spell, and is blinded for 1 minute.

Tentacle Whip. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 24 (3d10 + 8) slashing damage. If the target is a Huge or smaller creature (Gargantuan creature if the avatar has Growth Mutation), it is grappled (escape DC 25), pulled into an unoccupied space within 5 feet of the avatar, and must succeed on a DC 27 Intelligence saving throw or be stunned until this grapple ends. The avatar can’t use the same tentacle whip on another target until this grapple ends. The avatar has six tentacle whips. 

Extract Brain. Melee Weapon Attack: +17 to hit, reach 5 ft., one incapacitated creature grappled by the avatar. Hit: 118 (10d20 + 8) piercing damage. The excruciating pain of this action causes a creature to be unable to cast spells or activate magic items for 1 minute. If this damage reduces the target to 0 hit points, the avatar kills the target by extracting and devouring its brain. The avatar regains hit points equal the damage dealt and gains a bonus to its damage rolls equal to the slain creature's Intelligence modifier (minimum of 1) until it takes a short or long rest.

Shield of Thralls (5/Day). The avatar grants 20 temporary hit points to itself or to one creature of its choice within its telepathy range. If the target is a mind flayer, the amount of temporary hit points is doubled. If these temporary hit points are lost due to incoming damage, the shield bursts in a 10 foot-radius, forcing creature's hostile to mind flayers in the area to make a DC 24 Wisdom saving throw or be stunned until the end of its next turn.

Consuming Essence Wave (Mythic Only; Recharge 5–6). The avatar unleashes an essence devouring shockwave in a 120-foot cone. Creatures in the area must make a DC 27 Wisdom saving throw. On a failed save, if the creature has at least one unspent spell slot of a level less than or equal to 6, the avatar chooses one of those spell slots to consume. If the creature has no spell slots, the avatar instead consumes 6 of the creature’s hit dice equal. If the creature has no hit dice remaining, the creature gains a level of exhaustion instead. On a successful save, the creature is unaffected. After using this action, if the avatar consumed one or more spell slots or hit dice, it gains a mutation, as determined by rolling on the mutations table. 

When the avatar gains a mutation, roll 1d100 and add a bonus equal to the sum of all spell slot levels and hit dice consumed during the turn. Should you roll a mutation the avatar already has, reverse the digits and give the avatar the corresponding mutation instead, or roll again. Unless otherwise noted, the avatar retains each mutation for one hour. If a mutation’s entry doesn’t specify that it requires an action, reaction, or legendary action to use, it is a passive effect that lasts for the duration and doesn’t require concentration. For any mutation that enables the dragon to cast a spell, its spellcasting ability is Intelligence (See Monster Characteristics Description for mutations table).

OverMind Blast (Recharge 5–6). Creatures of the avatar's choice within 120 feet of it must succeed on a DC 27 Intelligence saving throw or take 76 (8d12 + 10) psychic damage and have the stunned condition for 1 minute. A stunned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature failed the saving throw by 7 or more, it is instead charmed by the avatar for 1 hour or until the target takes damage from the avatar or a mind flayer. The avatar can issue telepathic commands to the charmed creature (no action required), which it does its best to obey.

If this damage reduces a creature to 0 hit points, it dies and transforms into a Mind Flayer Clairvoyant under the avatar's control and acts immediately after it in the initiative order. The target can’t be returned to its original form by any means short of a wish spell.

Spellcasting (Psionics). The avatar casts one of the following spells, requiring no spell components and using Intelligence as the spellcasting ability (+19 to hit, save DC 27, +10 to all psychic and force damage rolls):

At will: detect magic, detect thoughts, dispel magic (6th level), scrying, Gravity Sinkhole, Gravity Fissure, Pulse Wave (5th level), Raulothim's Psychic Lance (7th level), Magnify Gravity (6th level), Tasha's Mind Whip (7th level), Vortex Warp (9th level), clairvoyance, confusion, dream

3/day each: counterspell (5th level), Maddening Darkness, Disintegrate (8th level), Synaptic Static, Teleport, Scatter, Wall of Force

1/day each: feeblemind, plane shift (self only), Ravenous Void, Dark Star, Psychic Scream, Gate

Psychic Link. The avatar targets one incapacitated creature it senses with its Creature Sense trait and establishes a psychic link with the target. Until the link ends, the avatar 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 avatar can terminate the link at any time (no action required). The target can use an action on its turn to attempt to break the link, doing so with a successful DC 25 Charisma saving throw. On a successful save, the target takes 20 (3d6 + 10) psychic damage. The link also ends if the target and the avatar are more than 100 miles apart. The avatar can form psychic links with up to two hundred creatures at a time.

Sense Thoughts. The avatar targets a creature with which it has a psychic link. The avatar gains insight into the target’s emotional state and foremost thoughts (including worries, loves, and hates).

Teleport. The avatar teleports, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied place that it can see.

Luck of the Far Realms. When the avatar makes a successful Attack Roll against a foe, it can change that hit into a Critical Hit.

Spell Mimicry. Immediately after a creature the avatar can see casts a spell of 9th level or lower, the avatar tries to copy the spell. That creature must succeed on a DC 25 Charisma saving throw, or the avatar immediately casts the same spell at the same level (+19 to hit with spell attacks, spell save DC 27), requiring no material components and choosing the spell’s targets.

The avatar can take 5 legendary actions, choosing from the options below. It can take only one legendary action at a time and only at the end of another creature’s turn. The avatar regains spent legendary actions at the start of its turn.

Attack. The avatar makes two attacks, using either his Dissonant Claw or Tentacle Whip.

Mindbreaker. The avatar targets a creature within 240 feet of itself and disrupts its mental processes, causing the target to have disadvantage on all ability checks, attack rolls, and saving throws until the end of the target’s next turn. If the target has a psychic link with the avatar, it also breaks any concentration it is maintaining on a spell or ability it has active. The creature also takes 12 (1d4 + 10) psychic damage per level of the spell or 13 (1d6 + 10) force damage times its proficiency bonus if it was an ability. Additionally, if the avatar's God-Brain's Descendant trait has been activated in the past hour, the target and enemies of the avatar within 45 feet of target take an additional 20 (3d6 + 10) psychic damage.

Sever Psychic Link. The avatar targets one creature within 240 feet of it with which it has a psychic link. The avatar 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. Additionally, if the avatar's God-Brain's Descendant trait has been activated in the past hour, the target also suffers the effects of the slow spell.

Suckle Lifeforce. The avatar’s tentacles release thorny protrusions, dealing 16 (2d8 + 8) piercing damage to all creatures currently grappled by it. The avatar regains a number of hit points equal to the total damage dealt. If the avatar's God-Brain's Descendant trait has been activated in the past hour, this damage is doubled.

Overpowering Mind (Costs 2 Actions). The avatar recharges its Mind Blast and uses it. A creature that fails the saving throw takes an additional 15 (1d10 + 10) psychic damage whenever it fails a saving throw for 1 minute.

Rend Reality (Costs 2 Actions). The avatar rips at the bonds of reality in its immediate area. Each creature within 20 feet of the avatar must succeed on a DC 24 Constitution saving throw or take 34 (4d12 + 10) force damage and gain 1 level of exhaustion. If a creature fails the saving throw by 5 or more, they are also subjected to the effects of the Reality Break spell.

Aberrant Shaper (Costs 3 Actions). The avatar makes a Tentacle Whip attack. If the strike hits, the creature takes no damage. Instead, it must succeed on a DC 23 Wisdom saving throw or it suffers the effects of the polymorph spell, except instead of becoming a Beast, the target becomes an Aberration of the avatar's choice (often choosing creatures that are created by mind flayers).

Brainstorm (Costs 3 Actions). The avatar casts lightning bolt (5th level, DC 23) three times, each bolt going in different directions. When a creature takes damage from the bolt, on a success or failure of the bolts saving throw, it becomes the initial target of the chain lightning (9th level, DC 25) spell. Multiple chains can be created in this way, but they still follow the rules of the spell.

If the avatar's "God-Brain's Descendant" trait has been activated in the past hour, it can use the following options as legendary actions.

Tentacled Fury (Costs 2 Actions). A plethora of additional tentacles emerge from the avatar. The next time it uses its Multiattack action, if it makes a Tentacle Whip attack, it makes one attack for each creature within 30 feet of itself. The avatar can grapple each target separately. After using this feature, any tentacles beyond its usual six disappear unless they’re grappling a creature.

A Thousand Unspeakable Horrors (Costs 3 Actions). Each creature of the avatar's choice that is within 30 feet of it and can see it must succeed on a DC 24 Wisdom saving throw or be overcome with blinding fear. On a failed save, the creature takes 32 (4d10 + 10) psychic damage and is frightened and blinded. On a success, it takes half damage and isn’t frightened. A creature can repeat the saving throw at the end of each of its turns, ending the frightened effect on itself on a success. The blinded effect is permanent, unless removed by a lesser restoration spell or similar magic. 

Brain Freeze (Costs 3 Actions). The avatar casts Rime's Binding Ice (9th level, DC 24) in a 30-foot-radius centered on itself. For 1 minute, in an area of a 30-foot-radius, 80-foot-high cylinder centered on the point where the avatar casted the ice, is under the effects of the Ice Storm (DC 25) spell. A creature that enters the area for the first time or starts its turn there must make the saving throw against the storm.

Psychic Gale Storm (Costs 4 Actions). The avatar wills such a powerful psychic wind from the Astral plane it manifests as a Whirlwind at a point within 120 ft. of the avatar (DC 24). All creatures that are subjected to the effects of the whirlwind must make a DC 25 Intelligence saving throw. On a failed save, a creature must roll on the mental effects table for psychic winds, described in chapter 2 of the Dungeon Master's Guide. 

Color Pools (Costs 4 Actions). The avatar tears at the fabrics of spacetime separating the planes of existence, creating 1d4 + 2 Color Pools (described in chapter 2 of the Dungeon Master's Guide) at random locations within 300 ft of the central point where the Astral Plane has merged with the Material Plane. A pool functions as and has the maximum dimensions of the Gate spell portal. Roll on the Astral Color Pools table for each pool to determine which color each one is, rerolling any duplicates. Theses pools remain for 1 minute, and whenever the avatar casts the spells Gravity Sinkhole, Gravity Fissure, Dark Star, Ravenous Void, or Vortex Warp, it can use one of these pools as the casting point, as if the avatar was in the pool's space.

Astral Invasion (Costs 5 Actions). The avatar wills the Astral plane to spit out some of its inhabitants to combat its enemies. Roll on the Wildspace, Astral Sea, and Ship Encounter tables (described in the Introduction: Creatures A to Z of Boo's Astral Menagerie in Spelljammers: Adventures in Space), once each. These summoned creatures will appear within 300 ft. of the central point where the Astral Plane has merged with the Material Plane and are enslaved to the avatar's will. When these creatures as slain, they vanish back into the Astral Plane, leaving no remains. The avatar can't use this legendary action again until all of its summoned creatures are slain. All summoned creatures return to the Astral plane when the avatar dies.