Legendary Resistance (5/Day)

If Beverley fails a saving throw, she can choose to succeed instead.

Whenever she does so, a nearby magical object screams, cracks, rusts or momentarily turns to rotting flesh.

The effect is cosmetic.

For now.

Archhag's Resistance

Beverley has advantage on saving throws against spells and magical effects.

Additionally, she cannot be transformed against her will, magically aged, or have her soul removed from her body while she has at least 1 hit point.

Elder Witch

Beverley's spells and abilities ignore resistance to necrotic damage.

A creature immune to necrotic damage instead has resistance to Beverley's necrotic damage.

Cruel Knowledge

Beverley immediately knows the following about every creature she can see:

• which creature has the lowest current hit points;
• which creature is concentrating;
• which creatures are under magical effects;
• which carried items are magical;
• which items require attunement;
• which creature is carrying the greatest number of magic items.

She does not know what an unidentified item does, but she knows its rarity.

This makes her frighteningly good at choosing targets.

Threefold Concentration

Beverley can concentrate on up to three effects simultaneously.

Whenever she takes damage, she makes one concentration saving throw for all effects.

Failure ends one effect of Beverley's choice for every 5 points by which she failed the DC.

The Black Rust

This is the mechanic I would make synonymous with Beverley.

When one of Beverley's abilities causes a magic item to become Corroded, place a Corrosion Counter on it.

Artifacts aren't destroyed by this feature, but can still be suppressed.

1 Counter — Tarnished

The item begins visibly decaying.

Weapons and armour lose 1 point of any numerical magical bonus they possess.

For other items, nothing mechanically happens yet.

2 Counters — Failing

The item's magical properties flicker.

At the start of each of its wielder's turns, roll a d6.

On a 1–2, the item's magical properties don't function until the beginning of that creature's next turn.

3 Counters — Ruined

Very rare or lower-rarity item:

Destroyed.

Its magic collapses permanently.

Legendary item:

It instead becomes Dormant and gains one additional Corrosion Counter.

4 Counters — Annihilated

A legendary magic item is destroyed.

Artifacts cannot gain more than 3 Corrosion Counters. At 3, the artifact is suppressed until Beverley dies.

Removing Corrosion

During combat, Greater Restoration removes one Corrosion Counter.

Wish removes all counters from one item.

Killing Beverley does not restore destroyed items.

Spellcasting

Beverley is a 20th-level spellcaster. Charisma is her spellcasting ability (spell save DC 27, +19 to hit).

She requires no material components.

At will:
counterspell, dispel magic, dimension door, greater invisibility, major image, misty step

3/day each:
dominate monster, finger of death, forcecage, maze, plane shift, reverse gravity

1/day each:
feeblemind, power word stun, time stop, weird

She can cast counterspell and dispel magic as though using an 8th-level spell slot without expending a use.

Multiattack

Beverley makes three Witch-Claw attacks.

She may replace one attack with Withering Hex.

Witch-Claw

Melee Spell Attack: +19 to hit, reach 10 ft., one target.

Hit: 17 (2d6 + 10) slashing plus 22 (4d10) necrotic damage.

If the target is concentrating, its concentration saving throw against this damage is made with disadvantage.

If Beverley scores a critical hit, she may also place one Corrosion Counter on one non-artifact magic item worn or carried by the target.

Withering Hex

One creature Beverley can see within 120 feet must make a DC 27 Constitution saving throw.

On a failure, the creature takes 45 (10d8) necrotic damage and becomes Withered until the end of Beverley's next turn.

While Withered:

• it cannot regain hit points;
• its speed is halved;
• it has disadvantage on Constitution saving throws.

On a successful save, the creature takes half damage and suffers no other effects.

Corrode the Precious

Recharge 4–6

Beverley points at one magic item she can see within 90 feet.

The creature carrying the item must make a DC 27 Charisma saving throw.

On a failure, the item gains 2 Corrosion Counters.

On a success, it gains 1 Corrosion Counter.

However, before making the save, its wielder can choose to protect the item with their own life force.

If they do:

The item gains no Corrosion Counters, and the creature takes

55 (10d10) necrotic damage.

This damage cannot be reduced, prevented, redirected or transferred.

Strip the Enchantment

Recharge 5–6

Beverley targets up to three creatures within 90 feet.

Each target must make a DC 27 Charisma saving throw.

On a failure, Beverley suppresses one magical effect currently affecting the creature until the end of Beverley's next turn.

She chooses the effect.

This can temporarily suppress things such as:

• Haste
• Holy Aura
• Foresight
• Bless
• Fly
• Shapechange
• magical flight granted by an item

It does not end the spell.

Hag's Exchange

Recharge 6

Beverley chooses two creatures she can see within 120 feet.

Each must succeed on a DC 27 Charisma saving throw.

If both fail, they instantly exchange positions.

They also exchange one condition currently affecting them, chosen by Beverley.

For example:

The poisoned fighter suddenly becomes fine.

The concentrating wizard standing beside them becomes poisoned.

Or the restrained character suddenly appears beside the Archhag while Beverley's intended victim appears trapped across the battlefield.

This does not transfer concentration itself.

Devour Spell

Beverley targets one spell effect of 8th level or lower within 60 feet.

The spell immediately ends.

Beverley regains 10 hit points per level of the spell.

A 9th-level spell requires Beverley to make a Charisma check against DC 19. On a success, it is also devoured.

Once Beverley successfully devours a 9th-level spell, she cannot use Devour Spell again until the beginning of her next turn.

Skitter Between Shadows

Beverley teleports up to 60 feet to an unoccupied space she can see.

Creatures adjacent to the space she leaves must succeed on a DC 27 Wisdom saving throw or be frightened of her until the end of their next turn.

Reactions

Beverley gets two reactions per round, but can only use one reaction per turn.

That distinction becomes extremely important at level 20.

Snip the Thread

When a creature Beverley can see within 90 feet activates a magic item or expends one of its charges, Beverley attempts to interfere with it.

The creature makes a DC 27 Charisma saving throw.

Failure:

• the item expends the charge/use normally;
• its effect doesn't occur;
• the item gains one Corrosion Counter.

Success:

The item functions normally.

Beverley can't use this reaction on artifacts.

Bad Luck, Darling

When a creature Beverley can see succeeds on an attack roll, saving throw or ability check, Beverley forces it to reroll the d20.

The second result must be used.

3/Day.

You Didn't Think I'd Let You Do That?

When a creature within 60 feet teleports, Beverley can use her reaction to redirect the teleport.

The creature appears at another unoccupied location of Beverley's choice within 60 feet of its intended destination.

A DC 27 Charisma saving throw negates this effect.

Yes.

This includes Misty Step.

Legendary Actions

Beverley can take 4 Legendary Actions per round.

Only one option may normally be used at a time and only at the end of another creature's turn.

She regains all spent Legendary Actions at the beginning of her turn.

Skitter

Beverley moves up to half her speed without provoking opportunity attacks.

Witch-Claw

Beverley makes one Witch-Claw attack.

Hex — Costs 2 Actions

Beverley uses Withering Hex.

Spoil Magic — Costs 2 Actions

One magic item Beverley can see within 60 feet flickers.

Until the beginning of Beverley's next turn, its magical properties are suppressed.

Artifacts are immune.

Delicious Despair — Costs 3 Actions

One creature within 90 feet must make a DC 27 Wisdom saving throw.

On a failure, it takes 36 (8d8) psychic damage and must immediately use its reaction, if available, to make one weapon attack or cast one cantrip against a creature of Beverley's choice.

Everybody Dance — Costs 4 Actions

Every creature of Beverley's choice within 60 feet must make a DC 27 Wisdom saving throw.

Failure:

The creature must immediately move up to its speed in a direction chosen by Beverley.

This movement provokes opportunity attacks normally.

Mythic Trait: You Thought THAT Was Beverley?

When Beverley is reduced to 0 hit points for the first time, she doesn't die.

Her body folds inward.

Bones snap.

Skin empties.

Her dress collapses onto the floor.

And from somewhere behind the party comes laughter.

“Oh, you precious little things.”

“You thought I was inside that?”

Every candle extinguishes.

Every reflective surface shows Beverley's face.

Every Corroded item begins screaming.

Beverley reappears in an unoccupied location within 120 feet.

She regains 350 hit points.

All conditions affecting her end.

All of her abilities recharge.

She gains the following abilities for the rest of the battle.

Beverley Unmasked

Aura of Ruination

A creature that starts its turn within 30 feet of Beverley takes 15 necrotic damage.

Additionally, magic items with at least one Corrosion Counter within the aura are visibly unstable.

Whenever their wielder rolls a natural 1 on an attack roll or saving throw, one such item of Beverley's choice gains another Corrosion Counter.

No More Resurrections

While Beverley Unmasked is alive, a creature that dies within 120 feet of her has its soul caught in her shadow.

Such a creature cannot be returned to life until either:

• Beverley dies, or
• the soul is wrested free.

A creature adjacent to Beverley can use an action to make a DC 25 Arcana, Religion or Athletics check.

On a success, one trapped soul is freed.

I particularly like this because she doesn't simply say “no resurrection.”

New Mythic Action

Rot Everything — Costs 4 Legendary Actions

Beverley unleashes a wave of black-green decay.

Every creature within 60 feet must make a DC 27 Constitution saving throw.

Failure:

55 (10d10) necrotic damage

and one magic item worn or carried by the creature gains one Corrosion Counter.

Success:

Half damage and no Corrosion.

Beverley then teleports up to 60 feet.

Once per round.