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Charybdis - AI-generated fantasy Monster

Charybdis

Sailors of the Sea of Monsters tell of a mouth beneath the waves that makes the ocean run uphill. They say the first sign is not a wave but a sudden slackening of every sail, followed by the sea draining toward a distant, impossible hole. Charybdis is a custom 5e interpretation of the mythic sea monster, designed as a high-level boss.

Monsters
Gargantuan monstrosity · CR 30 , deadly mythic solo encounter · Unique

Charybdis

A legendary sea monster whose cavernous mouth creates a living whirlpool, swallowing ships and turning the surrounding sea into a weapon.
AC23
HP676/676
CR30 , deadly mythic solo encounter
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 23 · HP 676 · CR 30 , deadly mythic solo encounter

Charybdis

Gargantuan monstrosity (titanic sea monster), chaotic evil
Armor Class23 (natural armor)
Hit Points676 (33d20 + 330)
Speed
Swim 120 ft.
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsStrengthDexterityConstitutionWisdomCharisma
SkillsPerception
Damage Resistances
Fire,
Lightning,
Thunder
Immunities
Acid,
Cold,
Poison,
Bludgeoning, piercing, and slashing damage from nonmagical attacks
Weaknesses
Charybdis cannot use Maelstrom Maw while incapacitated.
Sea-Bound Regeneration does not function outside the sea or while Charybdis is incapacitated.
Its immense size makes narrow passages and shallow water difficult terrain, and it cannot enter spaces too small to contain it.
Senses
Blindsight 120 ft.,
Darkvision 240 ft.,
Passive Perception 22
Languages
Understands Aquan and Primordial but cannot speak
Challenge30 , deadly mythic solo encounter
Proficiency Bonus+9
Saving Throw DC27
Legendary Resistance (3/Day). Charybdis has advantage on saving throws against spells and other magical effects. If it fails a saving throw, it can choose to succeed instead three times per day.
Amphibious. Charybdis can breathe air and water.
Titan of the Deep. Charybdis cannot be knocked prone or moved against its will while it is in the water. It has advantage on ability checks and saving throws made to resist being grappled or restrained.
Sea-Bound Regeneration. At the start of each of Charybdis's turns, it regains 30 hit points if it has at least 1 hit point and is in the sea. This trait does not function while Charybdis is incapacitated.
Mythic Might. Charybdis's attacks are magical.

Actions

Multiattack. Charybdis makes three attacks: two Crushing Fist attacks and one Bite attack.
Crushing Fist. Melee Weapon Attack: to hit, reach 30 ft., one target. Hit: 36 () bludgeoning damage. If the target is Huge or smaller, it must succeed on a Strength saving throw or be grappled (escape ). Charybdis can grapple up to two creatures at once.
Bite and Swallow. Melee Weapon Attack: to hit, reach 20 ft., one target. Hit: 42 () piercing damage plus 22 () acid damage. If the target is Large or smaller, it must succeed on a Dexterity saving throw or be swallowed. A swallowed creature is blinded and restrained, has total cover against attacks and effects outside Charybdis, and takes 35 () acid damage at the start of each of Charybdis's turns. Charybdis can have up to four creatures swallowed at once. If Charybdis takes 60 or more damage on a single turn from creatures inside it, it must succeed on a Constitution saving throw or regurgitate all swallowed creatures, which fall prone in an unoccupied space within 20 feet. If Charybdis dies, swallowed creatures are no longer restrained and can escape using 30 feet of movement, exiting prone.
Maelstrom Maw. Charybdis inhales seawater in a 120-foot-radius, 300-foot-deep cylinder centered on itself. Each creature and unsecured object in the area must make a Strength saving throw. On a failure, a creature takes 55 () bludgeoning damage, is pulled up to 100 feet toward Charybdis, and is restrained until the start of Charybdis's next turn. On a success, it takes half damage and is not pulled or restrained. A creature that hits Charybdis's mouth area, within 30 feet of its center, on a failed save is pulled into the mouth and takes an additional 22 () acid damage. Ships and structures in the area take 110 () bludgeoning damage, ignoring their damage threshold. Charybdis cannot use this action again until the start of its next turn.
Rending Surge. Charybdis slams the sea with its limbs. Each creature of its choice within 60 feet of it and in the water must make a Dexterity saving throw, taking 45 () bludgeoning damage and falling prone on a failure, or half damage without falling prone on a success. Each Huge or smaller vessel in the area takes 90 () bludgeoning damage.

Reactions

Surging Hide. When a creature Charybdis can see within 30 feet hits it with a melee attack, Charybdis forces that creature to make a Strength saving throw. On a failure, the creature takes 18 () bludgeoning damage and is pushed up to 20 feet away. If the creature is in the water, Charybdis can instead pull it up to 20 feet toward its mouth.

Legendary Actions

Undertow. Charybdis moves up to half its swimming speed without provoking opportunity attacks.
Crushing Fist. Charybdis makes one Crushing Fist attack.
Draw In (costs 2 actions). One creature Charybdis can see within 120 feet and in the water must succeed on a Strength saving throw or be pulled up to 60 feet toward Charybdis. This movement does not provoke opportunity attacks.
Rending Surge (costs 3 actions). Charybdis uses Rending Surge.
Role
Mythic solo boss, ship-wrecker, and battlefield controller
Built for
20

Notes for the game master

Custom 5e boss statblock, not a claim about official canonical statistics.
Charybdis has three legendary actions, choosing from the options above, at the end of another creature's turn. It regains spent legendary actions at the start of its turn.
Legendary Resistance (3/Day): If Charybdis fails a saving throw, it can choose to succeed instead.
The Maelstrom Maw area is centered on Charybdis and moves with it. Resolve ship damage using the vessel rules in the campaign, or use the listed damage as a direct structural hazard.

Tactics

  1. Opening

    Charybdis erupts beneath the largest vessel and immediately uses Maelstrom Maw, pulling combatants and ships toward its mouth before closing with a grapple and bite.

  2. Mid-fight

    Use Crushing Fist to seize front-line defenders and Rending Surge to punish clustered swimmers or damage vessels. Reposition through the water to keep multiple targets within the maw's reach.

  3. End of the fight

    At low hit points, Charybdis uses Maelstrom Maw to drag prey into the center, then bites creatures it has isolated. It fights to the death unless a divine force or a larger predator drives it away.

  4. Retreat

    Charybdis does not retreat from ordinary threats. If reduced below 100 hit points and confronted by a clearly superior supernatural power, it dives to the sea floor and abandons the immediate feeding ground.

How it fights

Use the whirlpool to separate characters from their ship and from one another.
Grapple creatures who approach the mouth, then bite or pull them into the vortex.
Use legendary movement to reposition between turns and keep swimmers within reach.
Do not keep every character in the water near the mouth; vary targets and let terrain, ships, and rescue choices matter.

Who it attacks first

Creatures operating the ship or protecting its crew
Flying or ranged combatants who can damage it without entering the water
Swimmers and creatures caught near the mouth
Healers or controllers attempting to free grappled allies

Works well with

A storm or enemy fleet can make escape difficult while Charybdis controls the immediate sea.
Smaller aquatic predators can pressure characters forced into the water, but should not obscure the boss encounter.
A nearby reef or wreck can provide cover from the whirlpool while also creating collision hazards.

How to beat it

Remain outside the 120-foot pull zone and attack from reliable flight or teleportation when possible.
A creature that can teleport out of a grapple or swallowed space can bypass much of its control.
Spread out to reduce the number of creatures caught by Rending Surge and avoid grouping near the vessel's center.
Use effects that restrain, stun, or incapacitate Charybdis to disrupt its actions, while accounting for its Legendary Resistance.
Protect or evacuate the vessel before combat, since the monster can destroy a ship faster than it can be repaired.

Ways to avoid a fight

Experienced sailors can attempt to chart its feeding cycle and cross the territory during the brief lull between vortices.
A party may bargain with a sea deity, oracle, or rival monster to redirect Charybdis away from a threatened port.
Rescuing survivors from a wreck field can reveal safe routes and the monster's pattern of movement.

Ecology

A Gargantuan, pallid mass rises from the sea, its ridged hide mottled with barnacles and shipwreck splinters. Its many rope-thick limbs churn the water while a cavernous, tooth-ringed mouth opens like a bottomless well. The sea visibly slopes toward that mouth, as if the horizon itself were being poured into it.

Behavior

It lies submerged until ships, large sea creatures, or magical disturbances draw near. Charybdis is ravenous and territorial, attacking anything it can pull within reach. It rarely pursues prey far from deep water.

How it lives

Charybdis consumes marine life, wreckage, and entire vessels. Its feeding creates temporary deep vortices that draw nutrients and smaller predators into its hunting grounds. It is solitary and leaves little usable territory for other megafauna.

Lair

Charybdis haunts a deep trench or the mouth of a narrow strait. Wrecks circle the trench's rim, and the current may reverse direction without warning. These are encounter features, not additional lair actions.

Habitat
The Sea of Monsters, deep ocean trenches, violent straits, and waters surrounding cursed islands.

Signs that it is near

Currents draw toward a patch of open sea even against the prevailing wind.
Barnacle-encrusted wreckage circles a deep, apparently bottomless trench.
Fish and seabirds flee an area whose water has begun to rotate.
A low sucking roar travels through a ship's hull before the surface disturbance is visible.

Tags

mythic,
sea monster,
solo boss,
whirlpool,
ship hazard

Lore

Sailors of the Sea of Monsters tell of a mouth beneath the waves that makes the ocean run uphill. They say the first sign is not a wave but a sudden slackening of every sail, followed by the sea draining toward a distant, impossible hole. Charybdis is a custom 5e interpretation of the mythic sea monster, designed as a high-level boss.

What drives it

Hunger and territorial dominance drive Charybdis. It seeks dense concentrations of living prey and will attack vessels that cross its feeding grounds.

After the fight

When Charybdis dies, the sea around it boils and then falls unnaturally still. The whirlpool drains away over several minutes, revealing wreckage, swallowed treasure, and perhaps survivors trapped in air pockets beneath its body.

“They say the first sign is not a wave but a sudden slackening of every sail, followed by the sea draining toward a distant, impossible hole.”
From its lore

Variants

Storm-season Charybdis: Its Maelstrom Maw also deals lightning damage to creatures wearing metal armor, but it has no Sea-Bound Regeneration outside a storm.
The Bell-Burdened Charybdis: A massive enchanted bell is lodged in its throat. Ringing the bell can interrupt one use of Maelstrom Maw, but alerts the monster to the source.

Hooks

Plot hooks

A fleet disappears in waters that have been calm for weeks, leaving a single ship stranded far inland by a receding tide.
A coastal oracle demands the return of an ancient bell lodged inside Charybdis before a prophecy can be fulfilled.
A rival sea power has driven Charybdis toward a busy trade route, and the party must stop the migration before the next convoy sails.

How to use it

Run the encounter as a moving hazard across open water, not merely as a large creature on a flat battlefield.
Give the party a clear warning through currents, wreckage, and a visible funnel in the sea before the first pull.
Make the ship, nearby reefs, and distance from shore meaningful objectives alongside reducing Charybdis's hit points.
For a deadly level 20 encounter, provide room to maneuver and clear rules for how the whirlpool interacts with the party's vessel.

Treasure

Coins, weapons, and relics from wrecked vessels trapped in the trench.
A legendary item swallowed by Charybdis, recoverable from its body after the battle.
A hoard of pearls, coral, and sea-glass gathered unintentionally among its wreckage.

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