If the tarrasque fails a saving throw, it can choose to succeed instead.

Your Strength score increases by 4 and your Constitution score increases by 4. The upper cap on both these scores is 30 for you.

You reach maturity as a member of you other race would, you cannot die from old age, or otherwise. When you die, after 24 hours you retreat into the earth for at least a decade. Any equipment you were carrying comes with you, and any magic items attuned to you do as well, even if not on your person. All these objects come with you. Additionally, dying could cause the Tarrasque to spawn at DM discretion.

Your base walking speed is 30 feet. As a tarrasque your base walking speed is 40.

Any time the tarrasque is targeted by a magic missile 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.

• Attack.The tarrasque makes one claw attack or tail attack.
• Move.The tarrasque moves up to half its speed.
• Chomp (Costs 2 Actions).The tarrasque makes one bite attack or uses its Swallow.

The tarrasque can use its Frightful Presence. It then makes five attacks: one with its bite, two with its claws, one with its horns, and one with its tail. It can use its Swallow instead of its bite.

Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: (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

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

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

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

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.

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.

You can become a smaller Tarrasque. Abilities of this form are outlined below. You can become a Medium Tarrasque at Level 1, a Large Tarrasque at level 3, a Huge Terasque at level 5, a Gargantuan Tarrasque at level 11, a Colossal Tarrasque at level 15, and a Titan Tarrasque at level 20. You can transform once per short rest. Your Physical Stats change to be equal to the Tarrasque-the number of sizes under gargantuan, or +1 for Colossal and +2 for Titan.

Regeneration. Nonmagical weapons deal nonlethal damage to a were-tarrasque, regular, non-magical fire, acid, etc. does not harm you, nor does fall damage. You cannot drown or suffocate. A were-tarrasque has regeneration equal to its level, and it regains hit points at the beginning of its turn. This is not in effect when it is at full health

Increase base classes’s racial HD size up to d10 if it was lower, if not, it remains the size it was.