Thurin-Gud The Writhing Foe

Gargantuan monstrosity (Hydra half-dragon), unaligned

Armor Class 19 (Natural Armor)

19 (Natural Armor) Hit Points 475 (30d20 + 175)

475 (30d20 + 175) Speed 30 ft., swim 30 ft.

STR DEX CON INT WIS CHA 24 (+7) 14 (+2) 24 (+7) 16 (+3) 12 (+1) 14 (+2)

Condition Immunities Stunned

Stunned Damage Resistances Cold; Bludgeoning, Piercing, and Slashing from Nonmagical Attacks

Cold; Bludgeoning, Piercing, and Slashing from Nonmagical Attacks Damage Immunities Fire

Fire Senses Darkvision 60ft.,Passive Perception 18

Darkvision 60ft.,Passive Perception 18 Languages Abyssal, Draconinc, Common (telepathic)

Abyssal, Draconinc, Common (telepathic) Challenge 16 (15,000 XP)

Hold Breath. The hydra can hold its breath for 1 hour.

Multiple Heads. The hydra has six heads. While it has more than one head, the hydra has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Whenever the hydra takes 30 or more damage in a single turn, one of its heads dies. If all its heads die, the hydra dies.

At the end of its turn, it grows two heads for each of its heads that died since its last turn, unless it has taken acid damage since its last turn. The hydra regains 15 hit points for each head regrown in this way.

Reactive Heads. For each head the hydra has beyond one, it gets an extra reaction that can be used only for opportunity attacks.

Wakeful. While the hydra sleeps, at least one of its heads is awake.

Legendary Resistance (2/Day). If the Hyrdra fails a saving throw, it can choose to succeed instead.

Actions

Multiattack. The hydra makes as many bite attacks as it has heads.

Bite. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 10 (1d10 + 7) piercing damage. If the same target is hit by two or more bite attacks, the target is grappled by the hydra.

Steam Breath (Recharge 5-6). The Hydra must have three heads come together to exhale scalding steam in a 60-foot cone, for each additional head above three the damage increases by 1d6. Each creature in that area must make a DC 16 Dexterity saving throw, taking 46 (12d6) fire damage on a failed save, or half as much damage on a successful one.

Fling. One Large or smaller object held or creature grappled by the hydra is thrown up to 40 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 16 Dexterity saving throw or take the same damage and be knocked prone.

Legendary Actions

The hydra can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The hydra regains spent legendary actions at the start of its turn.

Detect. The hydra makes a Wisdom (Perception) check.

Bite/Fling. The hydra can make two bite attacks against different creatures within reach, or fling one grappled creature.

Grapple. (Costs 2 actions) The hydra can make one bite attack and attempt a grapple if successful the grappled target is lifted 15ft in the air.