Apex Tarrasque

Legendary Resistance (5/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. 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.

Regenerative Carapace. The tarrasque regains 30 hit points at the start of each of its turns. The tarrasque only dies when it starts its turn at 0 hits points and doesn't regenerate.

Enhanced Attacks. The tarrasque's attacks are magical for the sake of overcoming resistances and immunities.

Apex Siege Monster. The tarrasque deals double damage to objects, structures, vehicles, and creatures that are huge or larger.

Multiattack. The tarrasque can use its Frightful Presence. It then makes up to 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 and its hurl instead of its claws and horn.

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 15ft., one target. Hit: 28 (4d8 + 10) slashing damage.

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

Hurl. The tarrasque picks up part of the environment and throws it to a creature or point it can see within 600 feet of itself. All creatures within 30 feet of the target must make a DC 27 Dexterity save. On a failed save, a creature takes 8d8 bludgeoning damage or half as much on a success. Objects and structures automatically fail the saving throw.

Depending on the environment, this action may deal an additional 8d8 damage of an appropriate damage type to the environment the tarrasque is located (Fire for a volcanic region or Avernus, cold for an arctic region or Stygia, necrotic for the Shadowfell or a necromancer's lair, etc.)

Tail. Melee Weapon Attack: +19 to hit, reach 20ft., 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.

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

Attack. The tarrasque makes one claw attack or tail attack.

Move. The tarrasque moves up to half its speed.

Escape (Costs 2 Actions). The tarrasque attempts to break any bindings that are holding it.

Leap (Costs 2 Actions). The tarrasque bounds into the air and lands at a point it can see within 30 feet of itself. Everything within 30 feet of the tarrasque as it lands must make a DC 27 Strength saving throw. If a creature shares a space with the tarrasque as it lands, it makes this saving throw as disadvantage. On a failed save, a creature takes 10d6 Bludgeoning damage and is flung 30 feet away from the tarrasque and lands prone. On a success a creature takes half as much damage and isn't flung back.

Chomp (Costs 2 Actions). The tarrasque makes one bite attack or uses its Swallow.