Sesshoseki 殺生石

Large object (undead spirit), unaligned

Armor Class 17 (natural armor, hardened lava)

Hit Points 75 (10d10 + 20)

Speed 0 ft. (immobile)

STR 20 (+5) · DEX 1 (−5) · CON 15 (+2) · INT 12 (+1) · WIS 14 (+2) · CHA 16 (+3)

Saving Throws Con +5, Wis +5

Damage Vulnerabilities thunder (shatters the crust)

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

Damage Immunities poison, psychic

Condition Immunities blinded, charmed, deafened, exhaustion, frightened, paralyzed, petrified, poisoned, prone, restrained

Senses blindsight 60 ft. (creatures in the miasma only), passive Perception 12

Languages telepathy 60 ft. (understands Common and Infernal)

Challenge 3 (700 XP)

Traits

Immovable Monolith. The Killing Stone can’t be pushed, pulled, or knocked prone. If it is ever reduced to 0 hit points, the bound spirit is released as a CR 8 nine-tailed fox oni at DM discretion.

Toxic Miasma. A 20-foot-radius invisible cloud of noxious sulfur surrounds the stone. A creature that enters the aura for the first time on a turn or starts its turn there must make a DC 14 Constitution saving throw, taking 14 (4d6) poison damage on a failed save or half as much on a successful one. A creature that fails this save by 5 or more is also poisoned for 1 minute.

Actions

Malevolent Pulse (Recharge 5–6). The spirit within the stone releases a burst of dark ki in a 30-foot cone. Each creature in that cone must make a DC 14 Wisdom saving throw, taking 18 (4d8) necrotic damage on a failed save or half as much on a success. A creature that fails is also frightened of the stone until the end of its next turn.

Reactions

Toxic Reflux. When the stone takes thunder damage, it erupts. Each creature within 10 feet must succeed on a DC 14 Dexterity saving throw or take 7 (2d6) acid damage and be pushed 5 feet away from the stone.

Lore

The Killing Stone, home to a malevolent spirit that slays anyone who touches it.

Sesshoseki, or the “Killing Stone,” is a cursed object that serves as a spiritual prison for an extraordinarily powerful and malicious being. Its name comes from its ability to kill any living creature that draws near or touches the boulder’s surface. The danger is two-fold: first, the physical stone, saturated with negative energy; second, the spirit sealed inside it, believed to be the legendary nine-tailed fox Tamamo-no-Mae. Folklore says that after this fox died, her body turned to stone, and her vengeful spirit, Hoji, fused with the rock forever, turning it into a source of ceaseless malevolent energy known as jãki.

The stone sits in the volcanic region of Nasu, Tochigi Prefecture, at the foot of Mount Chausu, near the Nasu-Yumoto hot springs. The local geology amplifies the threat: cracks in the rock constantly vent hydrogen sulfide and sulfur dioxide, accounting for the deadly fumes around the boulder. Legend treats these gases as the tangible form of the poison the demon continues to spew even after death. A barren field stretches around Sesshoseki, traditionally viewed as the boundary of the realm of the dead. For centuries the stone has been kept under ritual guard: a sacred rope is strung around it, meant both to contain the evil power and to warn travelers of the mortal danger.

From Yokai Bestiary 5E, Book Two, p. 80 · Fern Flower Press