Gwisusan 귀수산

Gargantuan celestial, lawful good

Armor Class 20 (natural armor)

Hit Points 352 (22d20 + 132)

Speed 20 ft., swim 60 ft.

STR 28 (+9) · DEX 6 (−2) · CON 23 (+6) · INT 16 (+3) · WIS 21 (+5) · CHA 20 (+5)

Saving Throws Con +13, Wis +12, Cha +12

Skills History +10, Insight +12, Perception +12, Religion +10

Damage Resistances acid, cold, fire, lightning; bludgeoning, piercing, and slashing from non-magical attacks

Damage Immunities poison

Condition Immunities charmed, frightened, paralyzed, poisoned, prone

Senses blindsight 60 ft., passive Perception 22

Languages all, telepathy 120 ft.

Challenge 18 (20,000 XP)

Traits

Legendary Resistance (3/Day). If Gwisusan fails a saving throw, it can choose to succeed instead.

Mountainous Shell. The terrain of Gwisusan’s back counts as difficult terrain for other creatures. While at least one Huge or smaller creature stands on its shell, Gwisusan has half-cover against attacks and effects that originate off its shell (AC 22).

Calming Presence. Hostile creatures that start their turns within 60 feet of Gwisusan must succeed on a DC 20 Wisdom saving throw or have disadvantage on attack rolls against targets other than Gwisusan until the start of their next turn. A creature that succeeds is immune to this aura for 24 hours.

Magic Resistance. Gwisusan has advantage on saving throws against spells and other magical effects.

Innate Spellcasting. Gwisusan’s spellcasting ability is Wisdom (spell save DC 20). It can innately cast the following spells, requiring no material components:

At will: calm emotions (PHB, p. 221/249), control water (oceans only; PHB, p. 227/256)

3/day each: tidal wave (XGE, p. 168), dispel evil and good (PHB, p. 234/263), mass cure wounds (PHB, p. 258/296)

1/day each: control weather (PHB, p. 228/257), tsunami (PHB, p. 284/336)

Actions

Multiattack. Gwisusan makes three Shell Smash or Bite attacks in any combination.

Bite. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 31 (4d10 + 9) piercing damage.

Shell Smash. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 25 (3d8 + 9) bludgeoning damage, and the target must succeed on a DC 20 Strength saving throw or be pushed up to 20 feet and knocked prone.

Wavebreaker Roar (Recharge 5–6). Gwisusan releases a thunderous bellow that manifests as a 90-foot cone of concussive force. Each creature in the area must make a DC 20 Constitution saving throw, taking 54 (12d8) thunder damage on a failed save, or half as much on a success. A creature that fails is also deafened and stunned until the end of its next turn. The roar automatically disperses fog, cloud, and similar effects in the area.

Reactions

Shell Interpose. When a creature Gwisusan can see within 15 feet would take damage, Gwisusan may pivot, granting that creature three-quarters cover against the triggering effect.

Lore

A gigantic turtle bearing a mountain on its shell; artifacts and magical items are said to lie

In one alternate strand of the legend, once the Sinmun king departs for Kamunsa Temple, a powerful rival clan sets sail for the island that has recently drifted up to the coast. Rumor says they’re savage enough to kill the king if it serves their purposes. Your party’s task is to keep history on its proper course and prevent this clan from seizing the artifacts. Perhaps you’ll figure out how to negotiate with the dragon guarding the mountain—or with Gwisusan himself.

Turtle Mountain 7. Gwisusan, the Turtle Mountain (귀수산) — A gigantic turtle bearing a mountain on its shell; artifacts and magical items are said to lie upon that very peak.

From Korean Bestiary 5E, p. 56 · Fern Flower Press