Brylla, Hag of the Frozen Wastes

Graystaff Magic. Brylla carries a graystaff, a length of gray wood that is a focus for her inner power. She can ride the staff as if it were a broom of flying. While holding the staff, she can cast additional spells with her Innate Spellcasting trait (these spells are marked with an asterisk). If the staff is lost or destroyed, Brylla must craft another, which takes a year and a day. Only a bheur hag can use a graystaff.

Cloak of Brown Mold. Focusing her twisted magics onto the heart of an ice troll, brown mold has sprouted out of it to form a protective cloak. While wearing the cloak, Brylla's AC increases to 19, she gains immunity to fire damage, and her Strength score increases to 16 (from 13). Additionally, when a creature moves to within 5 feet of Brylla for the first time on a turn or starts its turn there, it must make a DC 12 Constitution saving throw, taking 11 (2d10) cold damage on a failed save, or half as much damage on a successful one.

Ice Walk. Brylla can move across and climb icy surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice or snow doesn’t cost her extra movement.

Regeneration. Brylla regains 10 hit points at the start of her turn as long as she's wearing the Cloak of Brown Mold. If Brylla takes damage from Harlequin's Hearthflame, this trait doesn't function at the start of her next turn. Brylla dies only if she starts her turn with 0 hit points and doesn't regenerate.

Innate Spellcasting. Brylla’s innate spellcasting ability is Charisma (spell save DC 15, +6 to hit with spell attacks). She can innately cast the following spells, requiring no material components:

At will: hold person,* ray of frost

3/day each: cone of cold,* ice storm,* wall of ice*

1/day each: control weather, used only to conjure a blizzard

Frigid Form (1/day). Brylla can shape-shift herself into snow, melding herself into the snow beneath her, dropping her Cloak of Brown Mold, and gaining Total Cover. While in this form, Brylla's only method of movement is a Fly Speed of 30 feet, and she can only move through snow. Brylla's form is dispelled if she drops to 0 Hit Points or if she takes an action to dispel the form, otherwise it lasts for 1 hour.

Legendary Resistance (2/Day). If Brylla fails a saving throw, she can choose to succeed instead.

Multiattack. Brylla can use her graystaff to cast a spell. She then may make either one slam attack or two claw attacks.

Slam. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 16 (3d8 + 3) bludgeoning damage plus 7 (2d6) cold damage.

Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (2d6 + 1) slashing damage plus 3 (1d6) cold damage.

Maddening Feast. Brylla feasts on the corpse of one enemy within 5 feet of her that died within the past minute. Each creature of Brylla's choice that is within 60 feet of her and able to see her must succeed on a DC 15 Wisdom saving throw or be frightened of her for 1 minute. While frightened in this way, a creature is incapacitated, can’t understand what others say, can’t read, and speaks only in gibberish; the DM controls the creature’s movement, which is erratic. A 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’s saving throw is successful or the effect ends for it, the creature is immune to Brylla's Maddening Feast for the next 24 hours.

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

Slam Attack. Brylla makes a slam attack.

At-Will Spell. Brylla casts one of her at-will spells.

Hazy Step (Costs 2 Actions). Brylla casts Misty Step to teleport to a nearby heavily obscured area.