Volcanic Whale

Legendary Resistance (4/Day). If the Volcanic Whale fails a saving throw, it can choose to succeed instead.

Echolocation. The Devourer Whale has a 120ft Blindsight, but can't use it while deafened.

Keen Hearing. The whale has advantage on Wisdom (Perception) checks that rely on hearing.

Volcanic Armor. The Volcanic Whale, living inside lava, has built over time a natural armor made of solidied magma, this armor gives him resistance to normal non magical weapons as well as fire immunity. However, when the Volcanic whale is damaged by at least 40 Acid damage in a single round of combat, the Volcanic armor naturally dissolves, losing the resistance to non magical attack and lowering the AC by 10 for 4 rounds, until the armor reforms

Extremely Heavy. The Devourer Whale can survive for 3 hours on land. Every turn thereafter, the whale takes 10 bludgeoning damage for every turn it remains on land. This damage comes from its weight crushing it, so being magically lifted, being given a flying speed, or other means of the DM's discretion can prevent it. Additionally, the whale takes twice as much damage from falling, but if it falls onto a creature, that creature takes double the amount of bludgeoning damage.

Siege Monster. The Devourer Whale deals double damage to objects and structures.

Multiattack. The Devourer Whale makes one Bristle Chomp attack and two other attacks, using Lava Jet or Fluke in any combination.

Bristle Chomp. Melee Attack Roll: +14, reach 15 ft. Hit: 36 (4d12 + 10) Piercing damage, and the target has the Grappled condition (escape DC 20). Until the grapple ends, the target has the Restrained condition and can’t teleport.

Lava Jet (Recharge 5–6). Range Attack Roll: +14, reach 80 ft. Hit: 23 (2d12 + 10) Fire damage.

Fluke Slam. Melee Attack Roll: +14, reach 30 ft. Hit: 23 (3d8 + 10) Bludgeoning damage. If the target is a Huge or smaller creature, it has the Prone condition.

Volcanic Whirlpool. Strength Saving Throw: DC 19, each creature and each object that is in a 60-foot range from the Volcanic whale is affected. Failure: 10 (2d8) Force damage, and the target is forcefully moved towards the Volcanic whale for 30 feet. Success: Half damage only and 10 feet.

Swallow. Strength Saving Throw: DC 27, one Large or smaller creature Grappled by the Volcanic Whale (it can have up to six creatures swallowed at a time). Failure: The target is swallowed, and the Grappled condition ends. A swallowed creature has the Blinded and Restrained conditions and can’t teleport, it has Total Cover against attacks and other effects outside the Volcanic Whale, and it takes 28 (8d6) Acid damage and 28 (8d6) Fire damage at the start of each of the Devourer Whale’s turns.

If the Volcanic Whale takes 30 damage or more on a single turn from a creature inside it, the Volcanic Whale must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, each of which falls in a space within 10 feet of the Volcanic Whale and has the Prone condition. If the Volcanic Whale dies, any swallowed creature no longer has the Restrained condition and can escape from the corpse using 20 feet of movement, exiting Prone.

Legendary Action Uses: 3. Immediately after another creature’s turn, the Devourer Whale can expend a use to take one of the following actions. The Devourer Whale regains all expended uses at the start of each of its turns.

Volcanic Menace. The Volcanic Whale moves up to half its Speed, and it makes one Bristle Chomp or Fluke attack.

Lava-Splash Movement. The Devourer Whale moves half his Speed and after that jumps fowards for the remaining half of the speed. At the end of this movement, the Volcanic Whale, after the jump creates an instantaneous lava wave in a 80-foot circle and a 30-foot height originating from itself. Creatures caught by the lava wave are covered in lava and take lava damage at the start of their turn. All metal object become heated for 4 rounds, causing them to deal 9 (2d8) fire damage. The Devourer Whale can’t take this action again until the start of its next turn.