Ultimate Tarrasque

The ultimate tarrasque is a model of pure destruction, only awakening when the normal tarrasque is destroyed. In a blast of light and flame, it is born, necrotic energy shining in its eyes and reflecting the world around it in cold steel. It can speak, knows about the general energy of the cosmos, and is created to destroy. It may engage in conversation, but its unerring course is the destruction of its target (most often an entire plane of existence, but as it only has appeared once, it’s not completely known what its final goal is by NPCs.).

Wings spread from the monstrosity’s back, giving it the advantage of flight, and it knows the most powerful spells. Only a wish spell, cast against the creature’s will, can finally destroy it, and even then the tarrasque can again awaken. The creature is immortal, unbeatable, and above all, hellbent on terror and violence.

Stats
Proficient in all besides Charisma skills, +19 bonus to each

Resistant to force, psychic, and magical weapon damage

Immune to radiant, necrotic, fire, cold, lightning, and nonmagical weapon damage

Vulnerable to thunder damage

Immune to all conditions besides invisibility

Languages: all

Abilities
Reflective Carapace

Any time the tarrasque is targeted by a magic missle spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 5, the tarrasque is unaffected. On a 6, the tarrasque is unaffected, and the effect is reflected back at the caster as though it originated from the tarrasque, turning the caster into the target.

Special trait: Invincibility

The ultimate tarrasque’s rampage is only ever ended by the casting of a wish spell, which requires a DC 26 Arcana check to surpass its will, and puts it to sleep at 0 HP. Then, it recedes back into the form of the original tarrasque and sleeps for at least 1d20 + 50 years, although it can be awakened by the proper ritual (DM decides).

Innate Spellcasting

The tarrasque can use either Charisma, Wisdom, or Intelligence to cast its spells.

The monster has a spell save DC of 25 and a bonus of +19 to hit with spell attacks.

At will: chain lightning, destructive wave, fireball (6th level), banishing smite (5th level)

3/day: meteor swarm, create monster (1d10 young dragons, demons CR 15 or higher, or 1 elder elemental), wish

1/day: power word kill, mach spell

Special trait: Siege Monster

The tarrasque deals double damage to structures.

Necrotic Eye: The tarrasque can take a bonus action to force a creature to look into its eyes after taking more than 20 damage from it. When this happens, they must make a DC 20 Intelligence saving throw or take 10d6 necrotic and 10d6 psychic damage.

Fire Wings: The tarrasque can take a bonus action to, as it flies, deal 5d6 fire damage with its wings to everyone around it. This doesn’t stop it from using another bonus action on its turn.

Actions:

Multiattack: The tarrasque casts an at-will spell, attacks once with its bite, twice with its claws, once with its stomp, and once with its tail.

Bite: Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 36 (4d12 + 10) piercing damage. If the target is a creature, it is Grappled (escape DC 20). Until this grapple ends, the target is Restrained, and the tarrasque can't bite another target.

 

Claw: Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 28 (4d8 + 10) slashing damage.

 

Horns: Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 32 (4d10 + 10) piercing damage.

 

Tail: Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 24 (4d6 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be knocked prone.

 

Frightful Presence: Each creature of the tarrasque's choice within 120 feet of it and aware of it must succeed on a DC 17 Wisdom saving throw or become Frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the tarrasque is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the tarrasque's Frightful Presence for the next 24 hours.

 

Swallow: The tarrasque 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 tarrasque, and it takes 56 (16d6) acid damage at the start of each of the tarrasque's turns.

If the tarrasque takes 60 damage or more on a single turn from a creature inside it, the tarrasque must succeed on a DC 20 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 tarrasque. If the tarrasque 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:

It can take 5, which regen at the start of its turn.

Bite: The tarrasque bites.

Spell (2): The tarrasque can use an at will spell or a 3/day spell without expending a usage of the spell.

Move: The tarrasque moves up to its speed.

Swallow(2): The tarrasque uses its swallow.

Power Word (3): the tarrasque uses its choice of a power word.