Cognizant target: Mystra, The Mother of all Magic

Phase 2: Core Anti-Magic Shell. While in Phase 2, a 20-foot-radius sphere of absolute magic negation surrounds Mystra. Spells and other magical effects are suppressed within this radius, except for spells cast directly by Mystra herself.

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

Phase 3: Sovereign Anti-Magic Shell. A permanent 30-foot-radius sphere of absolute magic negation surrounds Mystra’s Gargantuan base, suppressing all external magical properties and spells. Spells cast by Mystra ignore this shell completely.

Multiattack (Phase 1). Mystra makes two attacks with her Arcane Lash or casts one prepared spell up to 7th level.

Arcane Lash. Melee Spell Attack: +15 to hit, reach 10 ft., one target. Hit: 21 (4d6 + 7) force damage.

Multiattack (Phase 2). Mystra makes two attacks with her Fractured Shard Cleave or casts one prepared spell up to 8th level.

Fractured Shard Cleave. Melee Spell Attack: +17 to hit, reach 15 ft., one target. Hit: 29 (4d10 + 7) force damage plus 11 (2d10) psychic damage.

Multiattack (Phase 3). Mystra makes three attacks: one with her Sovereign Crown Strike and two with her Core Discharges.

Sovereign’s Crown Strike. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 35 (4d12 + 9) slashing damage plus 26 (4d12) force damage. If the target is a creature, it must succeed on a DC 27 Strength saving throw or be knocked prone.

Core Discharge. Ranged Spell Attack: +19 to hit, range 150 ft., one target. Hit: 36 (5d10 + 9) force damage plus 14 (4d6) radiant damage.

Planar Matrix Teleport. Mystra targets a creature she can see within 120 feet that has spell slots or active magical enhancements. She instantly teleports to an unoccupied space adjacent to that target, bypassing any physical obstacles.

Phase 1 & 2: Counterspell. Mystra can cast Counterspell at 9th level without expending a spell slot. She can use this reaction exactly once per round in Phase 1, and up to three times per round in Phase 2, tracking her spent uses individually.

Phase 3: Absolute Counterspell (5/Round). Mystra can cast Counterspell at 9th level without expending a spell slot up to five times per round. She regains all spent uses at the start of her turn.

Mystra can take 4 legendary actions, choosing from the options below. Only one option can be used at a time and only at the end of another creature’s turn. She regains spent actions at the start of her turn.

• Sovereign Displacement. Mystra forces a target within 90 feet to make a DC 27 Intelligence save. On a failure, she swaps its position on the battlefield with another creature or a hazard zone.
• Weave Snipe (Costs 2 Actions). Mystra makes one Core Discharge attack.
• Spell Surge (Costs 3 Actions). Mystra casts one prepared spell from her list.

Phase 1: The Human Avatar (Medium Form) (AC22)

Mystra walks the battlefield in a slender, Medium-sized humanoid shell wrapped in shimmering arcane silks. In this form, she has an Armor Class of 22 and a +15 bonus to hit. She can cast spells up to 7th level seamlessly without any delay or slow casting times, though 8th and 9th level spells still require 1 round of active concentration to stabilize before they manifest. She moves with a walking speed of 30 feet and can deploy a precise Counterspell reaction exactly once per round.

• The Shatter Point: If she takes 333 total damage during this phase, or takes 150 or more damage in a single round of combat, her fragile physical avatar shatters, instantly forcing her into Phase 2.

Phase 2: The Fractured Divinity (Huge Form) (AC24)

Her humanoid shell cracks violently under the structural stress, exposing the blinding, raw deific energy surging beneath the surface as her form expands to Huge size. Her weapon attacks and spell modifiers spike to +17 to hit, her walking speed accelerates to 45 feet, and she gains a flying speed of 30 feet. She can now seamlessly cast spells up to 8th level without delay, can execute Counterspell exactly three times per round, and projects an active 20-foot-radius Anti-Magic Shell centered on her form.

• The Divine Ascension: If she takes an additional 333 damage during this phase, or takes 150 or more damage in a single round of combat, her mortal bindings fail entirely; her current hit points instantly reset back to her absolute maximum pool of 666 as she assumes her true, ultimate form.

Phase 3: The Sovereign Machine (Gargantuan Form) (AC26)

Mystra discards her flesh entirely, reverting to her true, primeval form: a monumental, feminine machine-like body of polished porcelain-white steel, crowned by a wide, crescent metallic blade that forms her head. Fused completely into the cosmic bedrock, her movement speed drops to 0, but her command over the weave achieves finality. She can cast all spells instantly without slow casting times, executes Counterspell up to five times per round, and projects an un-bypassable 30-foot-radius Anti-Magic Shell at all times. Furthermore, upon reaching phase 3, she restores her entire hit point pool to maximum, unless an ability explicitly prevents healing.