Clay Behemoth

Acid Absorption. Whenever the Behemoth would take Acid damage, it instead takes no damage and regains Hit Points equal to the Acid damage it would have taken, up to its Hit Point maximum.

Rainfed Regeneration. On initiative count 20 (losing initiative ties), while exposed directly to acid rain, the Behemoth regains 2d6 Hit Points. This is a special environmental effect of this encounter, not a separate source of acid damage against other creatures. Solid overhead cover prevents this healing.

Mutable Anatomy. The Behemoth can reshape its own clay body into enormous fists, tendrils, hammers, hooks and other crude structures. These transformations do not change its creature type, size, game statistics or occupied space.

Immutable Essence. The Behemoth cannot be transformed into another form by spells or magical effects.

Magic Resistance. The Behemoth has Advantage on saving throws against spells and other magical effects.

Clayling Limit. The Behemoth can maintain up to three Lesser Claylings simultaneously. A fourth cannot be created until another is destroyed. When the Behemoth is destroyed, any surviving Claylings immediately collapse into lifeless mud.

Multiattack. The Behemoth makes two attacks, using Crushing Hammer or Whiplash Limb in any combination.

Crushing Hammer. Melee Attack Roll: +12 to hit, reach 10 ft., one target. Hit: 6d6 + 7 Bludgeoning damage (average 28). A creature hit must succeed on a DC 20 Strength saving throw or have the Prone condition.
The Behemoth transforms its forearm into an immense hammer of compressed clay and rock, striking downward with enough force to crater the ground.

Whiplash Limb. Melee Attack Roll: +12 to hit, reach 20 ft., one target. Hit: 5d6 + 7 Bludgeoning damage (average 24.5). A Huge or smaller target is Grappled (escape DC 20), and the Behemoth can pull that creature up to 10 feet towards itself. It can maintain only one such grapple at a time and cannot use Whiplash Limb while maintaining that grapple.
An arm elongates into a thick, muscular tendril of wet clay, stretching across the battlefield to wrap around an opponent.

Hurl Spawn (Recharge 4–6). Ranged Attack Roll: +12 to hit, range 60/120 ft., one target. Hit: 6d4 + 7 Bludgeoning damage (average 22). Whether the attack hits or misses, one Lesser Clayling forms in an unoccupied space within 10 feet of the target, provided the Behemoth has fewer than three active Claylings. The Clayling takes its first turn on initiative count 10 of the following round.
The Behemoth tears a writhing lump from its own chest and launches it forward. Upon landing, the mass unfolds into a misshapen miniature humanoid.

Earthbreaker (Recharge 5–6). Each creature on the ground within 20 feet of the Behemoth must make a DC 20 Dexterity saving throw.

• Failure: 8d6 Bludgeoning damage (average 28) and the Prone condition.
• Success: Half damage, and the creature does not fall Prone.

The ground in the affected area becomes Difficult Terrain until cleared.

Absorb Slurry (Recharge 5–6). The Behemoth absorbs acidic mud within 10 feet of itself, regaining 3d8 Hit Points. It cannot use this action if no acid-contaminated mud is available.

Viscous Reformation (2/Day). When the Behemoth takes Bludgeoning, Piercing or Slashing damage, it can reduce that instance of damage by 3d6.
(Apply its damage resistance first, then this reduction).
Its body briefly liquefies around the incoming strike.