Legendary Resistance (6/Day). If the tarrasque fails a saving throw, it can choose to succeed instead.

Magic Resistance. The tarrasque has Advantage on saving throws against spells and other magical effects.

Reflective Carapace. If the tarrasque is targeted by a Magic Missile spell or a spell that requires a ranged attack roll, roll 1d6. On a 1–5, the tarrasque is unaffected. On a 6, the tarrasque is unaffected and reflects the spell, turning the caster into the target.

Death Aura.
At the start of each of its turns, each creature within 30 feet takes 21 (6d6) necrotic damage unless it is undead or a construct.

Horrid Regeneration.
It regains 50 hit points at the start of its turn if it has at least 1 hit point. It does not regenerate if it took radiant damage since its last turn.

Undying Resilience.
If the Undead Tarrasque would be reduced to 0 hit points, it instead drops to 1 hit point unless it was struck by radiant damage or the dispel evil and good spell in the same round.

Siege Monster. The tarrasque deals double damage to objects and structures.

Magic Weapons.
The Tarrasque’s weapon attacks are magical.

Multiattack.
The Tarrasque makes one bite attack, two claw attacks, one horn attack, and one tail attack.

Bite. Melee Weapon Attack: +19 to hit, reach 10 ft., one target.
Hit: 36 (4d12 + 10) piercing damage plus 14 (4d6) necrotic damage. If the target is a creature, it must succeed on a DC 27 Constitution saving throw or have its hit point maximum reduced by the necrotic damage taken.

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

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

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

Necrotic Breath (Recharge 5–6).
The Tarrasque exhales a wave of grave energy in a 90-foot cone. Each creature in the area must make a DC 26 Constitution saving throw, taking 88 (16d10) necrotic damage on a failed save, or half as much on a successful one. Nonmagical plants and corpses in the area instantly wither.

The Tarrasque 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.

• Attack. The Tarrasque makes one claw or tail attack.

• Swallow (Costs 2 Actions). The Tarrasque makes one bite attack against a Large or smaller creature it is grappling and swallows it on a hit. Inside, the creature takes 56 (16d6) acid damage + 21 (6d6) necrotic damage at the start of each of the Tarrasque’s turns.

• Deathquake (Costs 3 Actions). The Tarrasque slams the ground, creating a shockwave. Each creature on the ground within 60 ft. must succeed on a DC 25 Strength saving throw or take 31 (7d8) bludgeoning damage and be knocked prone.

n.

MYTHIC ACTION (Optional)

When reduced to 0 hit points for the first time, it collapses into a pile of bones and ichor — then rises again as a Skeletal Tarrasque at half health with resistance to radiant damage, losing Horrid Regeneration but gaining Bone Storm (Recharge 6):

Each creature within 60 ft. takes 45 (10d8) slashing damage (Dex DC 25 half).