Beast of the Deepest Depths

Gargantuan aberration, chaotic neutral

Armor Class 24 (natural armor)
Hit Points 700 (40d20 + 280)
Speed 30 ft., climb 30 ft., swim 150 ft.

STR	DEX	CON	INT	WIS	CHA
20 (+5)	30 (+10)	25 (+7)	8 (-1)	16 (+3)	22 (+6)

Saving Throws Dexterity +19, Wisdom +12
Skills Athletics +14, Perception +12, Stealth +19
Damage Resistances bludgeoning, piercing, or slashing damage from weapons that are not magic; acid, fire, lightning, necrotic, thunder
Damage Immunities cold
Condition Immunities frightened, prone
Senses darkvision 600 ft., blindsight 100 ft., passive Perception 22
Languages Aquan (can’t speak)
Challenge 29 (135,000 XP)

Special Traits

• Colossal Creature. Kaiju are creatures far larger than the scale of others. Conventional weapons, even highly-enchanted ones, lack the mass to deal serious wounds to a kaiju. The same is true for all but the mightiest spells. When a creature of Huge size or smaller deals damage to a kaiju with a weapon or feature, or with a spell of 8th level or lower, it deals half damage, which can be reduced further by resistance or saving throws. Siege weapons and creatures with the Siege Monster trait are treated like Gargantuan creatures. Gargantuan creatures and 9th-level spells (including lower-level spells cast with 9th-level slots) deal normal damage, which can be reduced further by resistance or saving throws. Kaiju deal double damage to objects and structures. They ignore normal difficult terrain, and treat thick forests, settlements, or mountains as difficult rather than impassable terrain.
• Amphibious. The Beast of the Deepest Depths can breathe both water and air.
• Evasion. If the Beast of the Deepest Depths is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, the Beast of the Greatest Depths takes no damage if it succeeds on the saving throw, and only half damage if it fails.
• Keen Scent. The Beast of the Deepest Depths has advantage on Wisdom (Perception) checks that rely on scent.
• Legendary Resistance (3/Day). If the Beast of the Deepest Depths fails a saving throw, it can choose to succeed instead.
• Magic Weapons. The Beast of the Deepest Depths’ weapon attacks are magical.

Actions

• Multiattack. The Beast of the Deepest Depths makes four attacks: one bite attack and three tentacle attacks.
• Bite. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 28 (4d6 + 10) piercing damage, and the creature must succeed on a DC 23 Constitution saving throw or suffer an additional 14 (4d6) piercing damage at the start of its next turn. If it receives any amount of healing before the start of its next turn, or if a creature uses an action and succeeds on a Wisdom (Medicine) check of DC 20, it does not suffer this damage.
• Tentacle. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 23 (3d8 + 10) bludgeoning damage, and the target is grappled (escape DC 24). The Beast of the Deepest Depths can grapple up to 8 creatures simultaneously, while still having tentacles free to attack and maneuver.
• Mighty Wave. In a large body of water, the Beast of the Deepest Depths creates a mighty wave, a watery wall 500 feet long, 100 feet high, and 60 feet thick. Each creature in the mighty wave’s area must succeed on a DC 24 Strength saving throw or take 39 (6d12) bludgeoning damage and be knocked prone. On a successful saving throw, this damage is halved and the creature is not knocked prone. At the beginning of each of the Beast of the Deepest Depths’ turns thereafter, the mighty wave moves 60 feet away from it. Any creature that is Huge or smaller in the mighty wave’s area is carried along with it and must make a new Strength saving throw or suffer the initial damage again. A creature can escape the mighty wave with a DC 24 Strength (Athletics) check. The mighty wave continues its movement until it reaches land or an obstruction larger than it is.

Legendary Actions

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

• Jet (Costs 2 Actions). The Beast of the Deepest Depths propels itself backwards, moving up to 1 mile in a straight line. This movement does not provoke opportunity attacks, and creates a Mighty Wave that moves in the opposite direction.
• Detect. The Beast of the Deepest Depths makes a Wisdom (Perception) check.
• Tentacle. The Beast of the Deepest Depths makes a tentacle attack.

About

The Beast of the Deepest Depths is the most dreaded creature of the seas, normally inhabiting lightless trenches. On the rare occasions that it rises, all who dwell in the waters, or sail upon them, quake in terror.

The Nameless Dread. A bone-deep dread and eerie stillness herald its coming, and towering waves mark its passage, but the Beast of the Deepest Depths has no name, for that would give another power over it.

Shipbreaker. The Beast of the Deepest Depths can ruin a fleet of stout ships as quickly as a child scatters playthings, leaving only flotsam behind. Some have surmised that the larger the fleet, the more likely it will attack. The drives that stir its thoughts are nearly impossible to comprehend, but it does rise to battle any being – mortal or otherwise – that seeks to control the seas.

Against Ships

The Beast of the Deepest Depths can grapple ships and tear them apart. As an action, it makes a Strength (Athletics) check opposed by the captain’s (or helmsman’s) Strength (water vehicles) or Wisdom (water vehicles) check. If the ship is smaller than Gargantuan, the captain’s ability check suffers disadvantage.

While a ship is grappled, the Beast of the Deepest Depths can attack creatures on deck or in the rigging with its tentacles. It attacks the ship’s hull with its bite, automatically hitting and dealing double damage (because the ship is a structure).

Breaking the grapple requires the captain (or helmsman) to succeed on a Strength (water vehicles) or Dexterity (water vehicles) check, opposed by the Beast of the Deepest Depths’ Strength (Athletics) check. Lesser kaiju deal double damage to objects and structures. They ignore normal difficult terrain.