Monster: Leviathan Dragon (5e) Guide for D&D

They are Amphibious in nature & The Leviathan exhales a stream of hot steam in a 120 foot cone.

The leviathan makes one bite attack against a Large or smaller creature it is grappling.

Gargantuan dragon, chaotic neutral

Armor Class: 23 (natural armor)
Hit Points: 546 (28d20 + 252)
Speed: 20 ft., Swim 50 ft.

STR – 30 (+10) • DEX – 14 (+2) • CON – 28 (+9) • INT – 18 (+4) • WIS – 14 (+2) • CHA – 22 (+6)

Saving Throws: Str +18, Dex +10, Con +17, Int +12, Wis +10

Skills: Insight +10, Intimidation +16, Nature +12, Perception +10

Damage Immunities: cold, lightning; bludgeoning, piercing, and slashing from nonmagical attacks.

Condition Immunities: frightened, paralyzed.

Senses: truesight 120 ft., passive Perception 20

Languages: understands Abyssal, Common, Celestial, Draconic, Infernal, and Primordial but can’t speak, telepathy 120 ft.

Challenge: 25 (75,000 XP)

Amphibious: The leviathan can breathe air and water.

Freedom of Movement: The leviathan ignores difficult terrain, and magical effect can’t reduce its speed or cause it to be restrained.

It can spend 5 feet of movement to escape from non-magical restraints or being grappled.

Legendary Resistance (3/Day): If the leviathan fails a saving throw, it can choose to succeed instead.

Siege Monster: The leviathan does double damage on objects and structures.


Multiattack: The leviathan uses its Frightful Presence. It then makes three attacks: one with its bite and two with its claws. It can use its Swallow instead of its bite.

Bite: Melee Weapon Attack: +17 to hit, reach 15 ft., one target Hit: 21 (2d10+10) piercing damage. If the target is a creature it is grappled (escape DC 20). Until the grapple ends, the target is restrained, and the leviathan can’t bite another target.

Claw: Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 17 (2d6 + 10) slashing damage.

Tail: Melee Weapon Attack: +17 to hit, reach 15 ft., on target. Hit: 19 (2d8 + 10) bludgeoning damage.

Frightful Presence: Each creature of the leviathan’s choice within 120 feet of the leviathan and aware of it must succeed on a DC 20 Wisdom saving throw or become frightened for 1 minute.

A creature can repeat the saving throw at the end of each turn, ending the effect on itself on a success.

If a creature’s saving throw is successful or the effects ends for it, the creature is immune to the Leviathan’s Frightful Presence for 24 hours.

Steam Breath (Recharge 5-6): The Leviathan exhales a stream of hot steam in a 120 foot cone.

Each creature in the area must make a DC 24 Dexterity saving throw, taking 42 (12d6) cold damage and 42 (12d6) fire damage on a failed save, or half as much on a successful one.

Swallow: The leviathan makes one bite attack against a Large or smaller creature it is grappling.

If the attack hits, the target takes the bite’s damage, the target is swallowed, and the grapple ends.

While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the leviathan, and it takes 42 (12d6) acid damage at the start of each of the leviathan’s turns.

If the leviathan takes 50 damage or more on a single turn from a creature inside it, the leviathan must succeed on a DC 25 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the leviathan.

If the leviathan dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Legendary Actions

The leviathan can take 3 legendary actions, choosing form 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 leviathan regains spent legendary action at the start of its turn.

Detect: The leviathan makes a Wisdom (Perception) check.

Tail Attack: The Leviathan make a tail attack.

Control Water (Costs 2 Actions): The leviathan casts control water with the bludgeoning damage of the whirlpool and to objects is increased to 6d8 rather than 2d8 (spell savs DC 21).

The leviathan maintains concentration and has advantage on Constitution saving throws to maintains it.

The leviathan is an immense dragon-like sea creature, 300 to 500 feet long. It is the lord of all seas and the intermediary between aquatic creatures and the gods.

Lair Actions

On initiative count 20 (losing initiativeties), the leviathan takes a lair action to cause one of the following effect; the leviathan can’t use the same effect two rounds in a row:

  • The leviathan causes a geyser to form and erupt scalding victims caught in it.

    A point within 120 feet of the leviathan that it can see has a fountain of scalding water bubble and shoot out from a 20 foot cylinder centered on that point.

    Each creature in that area must make a DC 15 Dexterity saving throw.

    A creatures takes 3d12 fire damage on a failed save, or half as much damage on a successful one.

    Additionally, the 20-foot cylinder area become difficult terrain for 10 minutes and any creature that passed through that area takes 1d10 fire damage from the boiling hot steam left.

  • The leviathan can flood any area it is a cave than it is filled to the top, but if it is a river or lake than every creature in a 30-foot radius must make a DC 15 Strength saving throw.

    On a success they are pushed to the 30 foot radius mark and a fail they are thrown to the edge of the river/lake.

    Anyone hit by this ability (anyone inside his lair or in a 120-foot radius) is submerged by 50 feet.

    The water drains out in 4 minutes and this action takes an entire turn for the leviathan.

    Any creatures on top of or grappled by the leviathan are not affected, and any creature above 30 feet of the water surface is not affected and the water lavel rises 30 feet.

  • The leviathan causes water to shape and thrash causing pain to creatures around it.

    A point within 120 feet of it that is on the ground or in a body of water becomes difficult terrain in a 30-foot radius, 5 feet deep of that point and any creature that starts its turn there must succeed a Strength saving throw (DC 21) or take 6d6 bludgeoning damage and be pulled up to 10 feet toward the center of that point.

  • Regional Effects

    The region containing a legendary leviathan’s lair is warped by the leviathans magic, which creates one or more of the following effects:

    • Water levels are raised by 30 feet within 6 miles of the leviathan’s lair.
    • Sea creatures are aggressive towards non-sea fearing creatures within 1 mile.
    • Trenches within 1 mile of the leviathan’s lair form portals to the Elemental Plane of Water, allowing creatures of elemental water into the world to dwell nearby.

    If the leviathan dies, these effects fade over the course of 1d10 days.