Heung-mu 흑무

Huge elemental, unaligned

Armor Class 16 (natural armor)

Hit Points 210 (20d12 + 80)

Speed 0 ft., fly 40 ft. (hover)

STR 6 (−2) · DEX 18 (+4) · CON 18 (+4) · INT 5 (−3) · WIS 15 (+2) · CHA 13 (+1)

Saving Throws Dex +9, Con +9, Wis +7

Skills Perception +7, Stealth +9

Damage Vulnerabilities lightning, thunder

Damage Resistances acid; bludgeoning, piercing, and slashing from nonmagical attacks

Damage Immunities poison

Condition Immunities charmed, exhaustion, grappled, paralyzed, petrified, poisoned, prone, restrained

Senses darkvision 120 ft., passive Perception 17

Languages understands Primordial but can’t speak

Challenge 14 (11,500 XP)

Traits

Amorphous. Heung-mu can occupy another creature’s space and move through openings as narrow as 1 inch wide without squeezing.

Flyby. Heung-mu doesn’t provoke opportunity attacks when it flies out of a creature’s reach.

Incorporeal Movement. Heung-mu can move through creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Stinking Miasma. A suffocating cloud extends 20 feet from Heung-mu in every direction. A creature that starts its turn in the cloud must succeed on a DC 17 Constitution saving throw or take 22 (4d10) poison damage and be poisoned until the start of its next turn. On a success, the creature takes half damage and isn’t poisoned. A strong wind (at least 20 mph) temporarily disperses the miasma in the affected area until the end of Heung-mu’s next turn.

Hidden Core. The first time Heung-mu would be reduced to 0 hit points by damage that isn’t lightning or thunder, it is instead reduced to 1 hit point.

Actions

Toxic Lash. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 23 (5d8 + 4) necrotic damage.

Condense (Recharge 5–6). Heung-mu compresses into a crushing sphere of darkness. Each creature of Heung-mu’s choice within 10 feet must make a DC 17 Constitution saving throw, taking 44 (8d10) necrotic damage and being stunned until the end of its next turn on a failed save, or half as much damage and not stunned on a successful one.

Bonus Actions

Shifting Vapor. Heung-mu becomes semitransparent until the start of its next turn. Attack rolls against it have disadvantage, and it has advantage on Dexterity (Stealth) checks made to hide during that time.

Reactions

Mist Step. When Heung-mu takes lightning or thunder damage, it can move up to its fly speed without provoking opportunity attacks.

Lore

A poisonous black fog; prolonged inhalation is fatal. On the road it looks like black smoke crawling along

The creature’s name comes straight from two Sino-Korean characters: 흑 (heung), “black,” and 무 (mu), “mist” or “fog.” Taken literally, Heung-mu is “the black fog.”

Heung-mu is not a gwishin (a human ghost). It never appears in human form and shows no interest in unfinished business or revenge. Neither is it a dokkaebi, the mischievous goblin of Korean lore that bargains, jokes, or hands out enchanted trinkets. The best fit is an incorporeal yokai: a bodiless predator whose very presence becomes more toxic the closer it drifts. Breathe its stinking vapor long enough and you die.

From Korean Bestiary 5E, p. 60 · Fern Flower Press