Baalphea

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

First Flame of Anarith (Mythic Trait; Recharges after a Short or Long Rest). Upon being reduced to 0 hit points the first time, Baalphea concentrates on the infernal fire within her, she regains all her hit points and flames race across her body, shedding bright light in a 30-foot radius and dim light for an additional 30 feet for the duration. 

While this is in effect she heals any fire damage she receives, gains immunity to cold damage, any creature that moves within 30 feet of her for the first time on a turn or ends its turn there takes 1d10 fire damage.

She can use her bonus action to create a line of fire 30 feet long and 10 feet wide extending from her in a direction you choose. Each creature in the line must make a DC 24 Dexterity saving throw. A creature takes 4d8 fire damage on a failed save, or half as much damage on a successful one.

Heiress of Hellfire. Baalphea's fire damage ignores all resistance and immunity.

Magic Resistance. Baalphea has advantage on saving throws against spells.

Master of Magic. Baalphea has advantage on saving throws to maintain concentration and only needs to roll if she takes more than 30 damage in a single hit.

Locus of the Astral Tide. Baalphea can concentrate on two spells simultaneously. 

Witch of the Wicked Blaze. Baalphea has 30 sorcery points which she can use in the following ways:

Recover Spell Slot - At a cost of 2 points for a 1st level spell slot, 3 points for 2nd, 5 for 3rd, 6 for 4th, 7 for 5th, 8 for 6th, 10 for 7th, 11 for 8th or 12 for 9th.

Meta magic - Baalphea has access to the following meta magic: 

Distant Spell -When you cast a spell that has a range of 5 feet or greater, you can spend 1 sorcery point to double the range of the spell. When you cast a spell that has a range of touch, you can spend 1 sorcery point to make the range of the spell 30 feet.

Empowered Spell -When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls. You can use Empowered Spell even if you have already used a different Metamagic option during the casting of the spell. 

Heightened Spell - When you cast a spell that forces a creature to make a saving throw to resist its effects, you can spend 3 sorcery points to give one target of the spell disadvantage on its first saving throw made against the spell. 

Quickened Spell -When you cast a spell that has a casting time of 1 action, you can spend 2 sorcery points to change the casting time to 1 bonus action for this casting.

Subtle Spell - When you cast a spell, you can spend 1 sorcery point to cast it without any somatic or verbal components.

Twinned Spell - When you cast a spell that targets only one creature and doesn’t have a range of self, you can spend a number of sorcery points equal to the spell’s level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip). To be eligible, a spell must be incapable of targeting more than one creature at the spell’s current level. For example, magic missile and scorching ray aren’t eligible, but ray of frost and chromatic orb are.

Seeking Spell - If you make an attack roll for a spell and miss, you can spend 2 sorcery points to reroll the d20, and you must use the new roll. You can use Seeking Spell even if you have already used a different Metamagic option during the casting of the spell.

Transmuted Spell - When you cast a spell that deals a type of damage from the following list, you can spend 1 sorcery point to change that damage type to one of the other listed types: acid, cold, fire, lightning, poison, thunder.

 Spellcasting. Baalphea is a 30th-level spellcaster. Her spellcasting ability is Charisma (spell save DC 27, +19 to hit with spell attacks). Baalphea has following spells prepared:

Cantrips (at will): fire bolt, blade ward, control flames, mage hand, minor illusion, prestidigitation, thaumaturgy, dancing lights, light

1st level (8 slots): absorb elements, bane, burning hands, chaos bolt, dissonant whispers, hellish rebuke, hex, shield, silvery barbs, searing smite, unseen servant, mage armor, magnify gravity, silent image, chromatic orb, command, detect magic

2nd level (6 slots): aganazzar's scorcher, arcanist's magic aura, blur, dragon's breath, enthrall, flame blade, flaming sphere, heat metal, mirror image, pyrotechnics, scorching ray,  vortex warp, misty step

3rd level (6 slots): ashardalon's stride, bestow curse, blink, counterspell, dispel magic, fast friends, fireball, fly, haste, slow, major image, thunder step, lightning bolt

4th level (6 slots): confusion, charm monster, banishment, dimension door, elemental bane, freedom of movement, greater invisibility, sickening radiance, summon elemental, wall of fire

5th level (6 slots): arcane hand, conjure elemental, antilife shell, destructive wave, dominate person, far step, hold monster, flame strike, immolation, synaptic static, wall of force, wall of light

6th level (5 slots): arcane gate, bones of the earth, chain lightning, contingency, disintegrate, eyebite, fizban's platinum shield, globe of invulnerability, instant summons, summon fiend

7th level (4 slots): crown of stars, delayed blast fireball, divine word, etherealness, fire storm, plane shift, power word pain, reverse gravity, teleport, tether essence

8th level (3 slots): antimagic field, clone, dark star, demiplane, feeblemind, dominate monster, incendiary cloud, mind blank, telepathy

9th level (2 slots): foresight, meteor swarm, ravenous void, wish

Spellcasting. Baalphea casts a cantrip or spell.

Baalphea's cantrips do extra damage as if they had scaled up two additional times, for example her Fire Bolt does 6d10 fire damage.

Rekindle the Flame. Baalphea pauses and refocuses her energy recovering 2 sorcery points.

Gaze of Impelidoth (5-6). Baalphea shoots out a beam of fire and light from her outstretched hands, anything in a 120ft long 10ft wide line from her takes 7d10 fire damage and 7d10 radiant damage unless they pass a DC 24 Dexterity saving throw, if they pass they only take half damage. Anyone within 60ft of the beam must make a DC 22 Constitution saving throw or be blinded until the end of their next turn by the flash of light emitted.

Overwhelming Sorcery. If Baalphea cast a cantrip as her action she may cast an additional cantrip as her bonus action.

Baalphea has two reaction but can only use one on each creatures turn.

Reactive Spellcasting. Baalphea can cast a cantrip or spell as an attack of opportunity, this spell must be a single target spell.

Baalphea 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. Baalphea regains spent legendary actions at the start of her turn.

Rapid Cantrip. Baalphea casts a cantrip

Spellcasting (Costs 2 Actions). Baalphea casts a spell.

Overheat (Costs 3 Actions). Baalphea choses one target within 90ft, they suffer 4d10 fire damage. On the next time Baalphea Activates this ability she can pick another target, or if she picks the same target they must make a DC 24 Constitution saving throw or detonate. If they fail the target takes 6d10 fire damage and all things within 30ft of them must make a Dexterity saving throw or takes 10d10 fire damage, if they pass they take half damage. Any Overheated creature that is hit by an explosion must make a DC 24 Constitution save or explode themselves.

After activating the First Flame of Baator trait Baalphea gains 2 more legendary actions to a total of 5 and gains the mythic actions below. 

Reignite Fire (Costs 2 Actions). Baalphea regains 2 sorcery points and casts a cantrip.

Forbidden Sun (Costs 5 Actions). Baalphea conjures a massive ball of plasma which slowly crashes into its target location this time in the following turn. A 20ft radius area is indicated as to where the impact will take place. Creatures within the impact area take 20d10 fire damage and an additional 100 arcane damage which can not be resisted or reduced in any way. Creatures within 60ft of the impact take 10d10 fire damage and 50 arcane damage. Creatures within 120ft take 5d10 fire damage and 25 arcane damage. Creatures that die from this are burned to ash and can only be resurrected by a wish, true resurrection or by divine intervention.