Rusted Wyrm

Gargantuan Construct, Neutral

AC: 20

Initiative: +6 (16)

HP: 231 (14d20 + 84)

Speed: 40 ft., swim 60 ft.

STR
25 (+7)
DEX
13 (+1)
CON
22 (+6)
INT
8 (-1)
WIS
14 (+2)
CHA
6 (-2)

Immunities: fire; poison

Condition Immunities: exhaustion; frightened; petrified; poisoned

Senses: Darkvision 120 ft., Passive Perception 12

Languages: Common, Draconic

CR: 14 (XP 11,500; PB +5)

Habitat: Coastal, Forest

Treasure: Individual

Legendary Resistance (3/Day).

If the Rusted fails a saving throw, it can choose to succeed instead.

Actions

Multiattack.

The Rusted makes two Bite attacks.

Bite.

Melee Attack Roll: +12, reach 20 ft. Hit: 29 (4d10 + 7) Piercing damage.

Steam Breath (Recharge 5-6).

Dexterity Saving Throw: DC 19, each creature and flammable object that isn't being worn or carried in a 60-foot Cone. Failure: 45 (7d12) Fire damage, and the target starts burning. Success: Half damage only. Failure or Success: Being underwater doesn't grant Resistance to this Fire damage.

Bonus Actions

Encasing Rust.

Constitution Saving Throw: DC 19, one creature within 20 feet of the Rusted. Failure: 14 (4d6) Poison damage, and the target has the Poisoned condition until the end of its next turn. While Poisoned, the target has the Paralyzed condition.

Find this creature in the encounter builder

Rusted Wyrm

Source: The Lost Library of Lethchauntos, p. 273 - Licenses and attribution