Legendary Resistance (3/day). When Auntie fails a saving throw, she can choose to succeed instead.
Innate Spellcasting. Auntie’s spellcasting ability is Charisma (spell save DC 17). She can innately cast the following spells, requiring no material components:
At will: booming blade (17th level),confusion, detect magic, disguise self, enemies abound
3/day each: dream, [spell[blight[/spell] hypnotic pattern, phantasmal killer, sleep (13d8)
1/day each: eyebite, legend lore, mental prison, scrying, weird
Magic Resistance. Auntie has advantage on saving throws against spells and other magical effects.
Nightmarish Rebirth (Mythic Trait; recharges after a short or long rest). If Auntie is reduced to 0 hit points, she doesn't die or fall unconscious. Instead her body rapidly expands and contorts, as shadowy appendages rip out of her. Her hit points are set to 163, her size becomes large, and she gains both a climbing speed and a flying speed of 60 feet, as large shadowy wings and scrabbling limbs spout out from her. Her strength score increases to 23 and she gains new attack actions.
Multiattack. Auntie makes two Nightmare Touch attacks. If she is in her nightmare form, she can make two claw attacks and a bite attack instead.
Claws. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 5 (1d6 + 2) slashing damage or 13 (2d6 + 6) slashing damage if she's in nightmare form.
Nightmare Touch. Melee Spell Attack: +9 to hit, reach 5 ft., one creature. Hit: 18 (4d6 + 4) psychic damage. If the target is unconscious, it takes an extra 10 (3d6) psychic damage and is cursed until the hag dies or the curse is removed. The cursed creature’s hit point maximum decreases by 5 (1d10) whenever it finishes a long rest.
Bite (Nightmare Form Only). Melee Weapon Attack: +11 to hit, reach 15 ft., one creature. Hit: 15 (2d8 + 6) piercing damage plus 7 (2d6) psychic damage.
Dream Eater. When an unconscious creature Auntie can see within 30 feet of her regains consciousness, she can force the creature to make a DC 17 Wisdom saving throw. Unless the save succeeds, the creature takes 11 (2d10) psychic damage, and Auntie regains hit points equal to the amount of damage taken.
Auntie 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. She regains spent legendary actions at the start of its turn.
Move. Auntie can move up to half her speed.
Attack. Auntie makes one melee attack.
Cast a Spell (Costs 2 Actions). Auntie casts a spell from her innate spellcasting list.
Conjure Nightmare (Costs 3 Actions). Auntie summons a Flying Horror in an unoccupied space within 60 feet of her and she can't summon another until this one dies.
If Auntie's mythic trait is active, she can use the options below as legendary actions for as long as she remains in her nightmare form.
Wing Attack. Auntie beats her wings. Each creature within 10 feet of her must make a DC 17 Dexterity saving throw or take 13 (2d8 + 4) bludgeoning damage. Auntie can then fly up to half her flying speed.
Conjure Greater Nightmare (Costs 2 Actions). Auntie summons a [monster[Gloomstalker[/monster] in an unoccupied space within 60 feet of her, and she can't summon another until this one dies.
Nightmarish Miasma (Costs 3 Actions). Each creature within 60 feet of Auntie must make a DC 17 Wisdom saving throw. On a failed save, a creature falls unconscious and is plagued by nightmares. While plagued by nightmares a creature cannot be awoken and takes 10 (3d6) psychic damage at the start of their turns. Auntie regains hit points equal to half the psychic damage dealt to all creatures plagued by nightmares. A creature can remake this saving throw at the end of their turn, ending the effect on a success. Once a creature suceeds on this saving throw they are immune to Auntie's Nightmarish Miasma for the next 24 hours.
Description
Efialtos is an ancient and powerful spirit, one of the Keres. She has dominion over nightmares and paranoia, and grows in strength when she spreads fear to others. Her goals are mysterious, maybe incomprehensible, but her recent growth and strength is undeniable.
Fighting Efialtos in a mythic encounter is equivalent to fighting two CR 15 monsters in the same encounter.
Lair and Lair Actions
Auntie's lair is a small cave sequestered high in a mountain, filled with trinkets and strange baubles. While in her lair, at initiative count 20, Auntie can invoke the ambient magic of the cave to use a lair action. She cannot use the same lair actions two turns in a row
- Auntie attempts to trap a creature she can see in a nightmare. A creature of her choice within 30 feet of her must make a DC 17 Wisdom saving throw. On a failed save they are filled with nightmarish visions, and become frightened for 1 minute.
- Auntie fills a creature see can see with intense paranoia. Auntie casts Enemies Abound. She does not need to concentrate on the spell when she casts it this way.
- Auntie confuses the minds of those around her. Auntie casts the Confusion spell. She does not need to concentrate on the spell when she casts it this way.