Miasmorne

Huge monstrosity, unaligned

Armor Class

19 (natural armor)

Hit Points

230 (20d12 + 100)

Speed

20 ft., burrow 20 ft.

Saves

Str +11, Con +10

Skills

Arcana +1, Athletics +16, Survival +5

Damage Immunities

acid, fire; bludgeoning, piercing, and slashing from nonmagical attacks

Condition Immunities

petrified

Senses

tremorsense 60 ft.

Languages

Challenge

16

Proficiency Bonus

+5

Acidic Attacks

If a creature takes acid damage from the miasmorne and that creature is wearing nonmagical metal armor, that armor is destroyed.

Acidic Hide

After a nonmagical metal weapon hits the miasmorne that weapon melts and is destroyed. Likewise, nonmagical metal ammunition that hits the miasmorne is destroyed.

Actions

Multiattack

The miasmorne makes three attacks using Bite, Flechette or a combination of the two.

Bite

Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 22 (3d10 + 6) bludgeoning damage plus 7 (2d6) acid damage. If the target is a Large or smaller creature, it has the grappled condition (escape DC 18). The miasmorne can't make Bite attacks while a creature is grappled in this way.

Flechette

Ranged Weapon Attack: +11 to hit, range 60/120 ft., one target. Hit: 16 (3d6 + 6) acid damage.

Flechette Spray (Recharge 5-6)

The miasmorne launches flechettes from its fins in a 90-foot cone in front of it. All creatures in the cone must make a DC 19 Dexterity saving throw, taking 21 (6d6) acid damage on a failed save, or half as much damage on a successful one.

Acidic Secretion (1/Day)

The miasmorne secretes an acidic solution, then sprays it around itself. All creatures in a 20-foot-radius sphere, centered on the miasmorne, mustmake a DC 19 Dexterity saving throw. Targets take 26 (4d12) acid damage on a failed save, or half as much damage on asuccessful one. All nonmagical metals within the radius thataren't being carried, as well as nonmagical metal items carriedor worn by creatures that failed the save, are destroyed.