Could I get feedback on this boss monster?

[FunSize]

Trying to make this a serious challenge for 6 9th level characters. I'm a little miffed at the number of Concentration spells on her list, but they're geared toward disabling one person while she engages everyone else, so hopefully it works. Her HP is also kinda low. Feedback appreciated.

Edit: Increased HP. Added Recharge to Abyssal Chord. Added Ancestral Orchestra quality and Move Ancestral Orchestra action. Changed Legendary actions.

Darkest Fox
Medium Humanoid (Tiefling)
HP: 245
Armor Class 18

Speed: 40ft, Fly 60ft

Str 10, Dex 18, Con 14, Int 14, Wis 18, Cha 20

Saving Throws: Dex +8, Con +5, Wis +8, Cha +11

Skills: Performance +11, Deception +11, Stealth +8, Acrobatics +8

Damage Resistances: Fire, Necrotic

Languages: Common, Abyssal

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Song of the Blood: The Darkest Fox's harp continuously plays haunting music without her having to touch it. Any creature starting their turn within 30ft of her must make a Wisdom saving throw (DC 16) or have disadvantage on all saving throws and attack rolls until the start of their next turn. Each turn a creature remain within range they may repeat their saving throw. This will not affect deafened creatures.

Ancestral Orchestra: the Darkest Fox is accompanied by five Ancestral Instruments. Each instrument is a tiny Construct with AC 20 and 45HP that occupies it's own square . Any time the Darkest Fox casts a spell, she may instead cast it as if it had originated from the Instrument's square. Each instrument may also maintain a spell that requires concentration. Dealing any damage to an instrument ends a spell it is maintaining as if the caster lost concentration. Ancestral Instruments do not take their own actions.

Legendary Resistance (2/day)

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Actions:

Multiattack: The Darkest Fox can use Abyssal Chord and make two Razor Whip attacks, or Move an Ancestral Instrument and make two Razor Whip attacks.

Razor Whip: Melee weapon attack (10ft reach) +9 to hit. Hit: 3d8 +4 slashing damage

Abyssal Chord (Recharge 5-6): all creatures within a 60ft cone make a Charisma saving throw (DC 18) and take 2d10 Psychic damage and be stunned until the end of their next turn. On a successful save creatures take half damage and are not stunned.

Move an Ancestral Instrument: Roll 1d4. The Black Fox may move that many Ancestral Instruments as if they had a Flight speed of 30ft.

Spellcasting: The Darkest Fox uses Charisma as her spellcasting stat (DC 18, +10 to hit with spell attacks)

Spells:


Cantrips: Vicious Mockery, Minor Illusion, Blade Ward

1st Level (4 slots): Dissonant Whispers, Hideous Laughter, Healing Word

2nd level (3 slots): Heat Metal, See Invisibility, Silence, Shatter

3rd Level (3 slots): Dispel Magic, Fear, Major Image

4th Level (3 slots): Compulsion, Dimension Door, Hallucinatory Terrain

5th Level (2 slots): Dominate Person, Hold Monster

6th Level (2 slots) Irresistible Dance, Mass Suggestion

7th Level (1 slot): Symbol

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Legendary actions: The Darkest Fox 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. The Darkest Fox regains spent legendary actions at the start of their turn.

Move: Move 40ft or fly 60ft.

Razor Whip

Legendary Spellcast: Cast any spell of 1-3rd level. Can spend two legendary actions to cast a 4th or 5th level spell.

[Unoriginal]

Sounds pretty nice. the Spellcasting should be on the special capacity part, though, not the Action one.

Personally, I would have given her a Legendary action to cast a spell, rather than do another Abyssal Chord. With the action economy she has right now, she most likely won't be able to do much spells before dying. Betting give her a legendary action that incentive her to use them.

For Song of the Blood, most effect like that have a "if you pass the save, you're immune to it for 24h" and "you get a save each round". Did you not add those conditions on purpose?

Abyssal Chord seems pretty OP to me. No recharge, at will, high DC 60ft cone that stun once per round minimum? It could destroy all the non-CHA-based PCs in a few rounds

Will it be a solo boss fight, or will she have minions? Minions will make her Concentration spells worthwhile.

Since she's facing 6 PCs, I recommend boosting her HPs to at least 200.

Also, no offense, but unless you want her to sound ridiculous/funny on purpose, you should give her a different name than "the Darkest Fox".

[FunSize]

Good call on Legendary Action for spellcasting, I'll make that change.

Song of the Blood was intended to require a save at the start of every turn. But it's a continuous effect, so the idea was just to make her difficult to melee. Most of the party is ranged, so this may not be OP.

200hp is good.

Abyssal Chord is now recharge 5-6 and no longer a Legendary Action option.

She will have some demons as minions (probably 3 big beefy ones).

The name is kinda a placeholder of sorts, this is an "ascended" form of an Evil Bard that got hopped up on forbidden magic. As the players encountered her before, she wore a black fox mask so they started calling her "the Black Fox" before they learned what her actual name was, and it stuck.