Bone Beast

Huge undead monstrosity, chaotic evil
CR 14 (11,500 XP)

DEFENSE

Armor Class 25 (bone plating)
Hit Points 486 (40d12 + 148)
Speed 40 ft., burrow 20 ft. (through rubble, bone, corpses)

Saving Throws Str +14, Con +12, Wis +8
Damage Resistances bludgeoning, piercing, slashing from nonmagical weapons
Damage Immunities poison, necrotic
Condition Immunities charmed, exhaustion, frightened, paralyzed, poisoned
Senses darkvision 120 ft., tremorsense 60 ft., passive Perception 12
Languages —
Proficiency Bonus +5

CORE TRAITS

Ossified Colossus

The Bone Beast is partially encased in layered bone armor.

• The Bone Beast has resistance to all damage while above half its hit points.

• When reduced below half HP, its bone plates crack and splinter, losing this resistance but gaining new offensive abilities.

Relentless Horror

When the Bone Beast is reduced to 0 hit points, it does not die immediately.

• It makes a DC 18 Constitution saving throw

• On a success, it drops to 1 HP instead and immediately takes a full turn

• This ability can trigger once per combat

Bonequake Movement

When the Bone Beast moves at least 20 ft. in a straight line, the ground shakes.

Creatures within 10 ft. of its path must succeed on a DC 18 Dexterity save or fall prone.

PHASE TWO: BROKEN BONE FRENZY

When the Bone Beast drops below 50% HP, its armor ruptures violently.

Frenzied State (Passive)

• Gains advantage on all melee attack rolls

• Movement speed increases by +20 ft.

• Multiattack increases by +1 attack

ACTIONS

Multiattack

The Bone Beast makes three attacks: two Claws and one Bite or Bone Slam.

(At half HP or lower, it makes four attacks.)

Claw

Melee Weapon Attack: +14 to hit, reach 15 ft., one target
Hit: 21 (3d8 + 8) slashing damage

• If both Claws hit the same creature in a turn, the target is grappled (escape DC 18)

Bite (Devouring Maw)

Melee Weapon Attack: +14 to hit, reach 10 ft., one grappled or prone creature
Hit: 32 (4d10 + 8) piercing damage + 10 (3d6) necrotic damage

The Bone Beast regains hit points equal to the necrotic damage dealt.

Bone Slam

Melee Weapon Attack: +14 to hit, reach 10 ft., one target
Hit: 28 (4d10 + 8) bludgeoning damage
Target must succeed on a DC 18 Strength save or be knocked prone.

Bone Shard Eruption (Recharge 5–6)

Jagged bone spikes explode outward from the Bone Beast’s body.

Creatures within 20 ft. must make a DC 18 Dexterity save:

• Fail: 35 (10d6) piercing damage and restrained by embedded bone

• Success: Half damage, not restrained

A restrained creature can use an action to make a DC 18 Strength check to free itself.

Consume the Fallen (Bonus Action)

The Bone Beast devours a corpse or unconscious creature within 5 ft.:

• Regains 30 HP

• Immediately makes one Claw attack

REACTIONS

Bone Rattle Retaliation

When hit by a melee attack, the Bone Beast may make one Claw attack against the attacker.

LEGENDARY ACTIONS (3/ROUND)

The Bone Beast can take 3 legendary actions, choosing from the options below:

• Move: The Bone Beast moves up to half its speed

• Claw Attack: Makes one Claw attack

• Bone Tremor (Costs 2 Actions): Each creature within 15 ft. must succeed on a DC 18 Dexterity save or be knocked prone

• Devour (Costs 3 Actions): Makes one Bite attack against a prone or grappled creature

MYTHIC ACTION

If reduced to 0 HP while Frenzied:

• Bone Beast explodes into fragments

• Reforms after 1 round with 120 HP

• Loses Legendary Actions

• Gains Bone Shard Eruption every round