Legendary Resistance (1/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.
Twin Monster. The tarrasque deals double damage to objects and structures when within a 40 ft range of its twin.
Multiattack. The tarrasque can use its Frightful Presence. It then makes four attacks: one with its bite, one with its claws, one with its horns, and one with its tail. It can use its Swallow instead of its bite.
Bite. Melee Weapon Attack: +12 to hit, reach 8 ft., one target. Hit: 36 (3d12 + 8) piercing damage. If the target is a creature, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the tarrasque can't bite another target.
Claw. Melee Weapon Attack: +12 to hit, reach 10ft., one target. Hit: 24 (3d8 + 8) slashing damage.
Horns. Melee Weapon Attack: +12 to hit, reach 10ft., one target. Hit: 30 (3d10 + 10) piercing damage.
Tail. Melee Weapon Attack: +12 to hit, reach 15ft., one target. Hit: 18 (3d6 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 15 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 10 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 28 (8d6) acid damage at the start of each of the tarrasque's turns.
If the tarrasque takes 40 damage or more on a single turn from a creature inside it, the tarrasque must succeed on a DC 18 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 1 legendary action, choosing from the options below. Its single legendary action option can be used only at the end of another creature's turn. The tarrasque regains its spent legendary action 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.
Chomp (Costs 2 Actions). The tarrasque makes one bite attack or uses its Swallow.
Lair and Lair Actions
The lair of an Ice Tarrasque is typically located within the upper-elevation levels of a mountain range. They make their dens within caverns of ice, most often in a leveled area surrounded with peaks or cliffs to provide shelter from the elements, as well as extra layers of defense. They will leave these caverns to hunt for prey, which after killing, they drag back into their den. As food is scarce in such an environment, they resist the urge to devour prey immediately, instead stretching its sustenance as long as possible.
On initiative count 20 (losing initiative ties), the tarrasque takes a lair action to cause one of the following effects; the tarrasque can’t use the same effect two rounds in a row:
- A small avalanche descends from a point on the perimeter of its lair within 120 feet of it, creating a 20-foot-high, 5-foot-wide descent of snow and ice that continues for 40 feet from its origin point. Each creature in the avalanche's area must make a DC 15 Dexterity saving throw, taking 21 (6d6) cold damage on a failed save, or half as much damage on a successful one.
- A tremor shakes the lair in a 40-foot radius around the tarrasque. Each creature other than the tarrasque on the ground in that area must succeed on a DC 15 Dexterity saving throw or be knocked prone.
- Arctic winds form a swirling cloud in a 15-foot-radius sphere centered on a point the tarrasque can see within 180 feet of it. The sphere spreads around corners, and its area is lightly obscured by a whirlwind of snow. It lasts until initiative count 20 on the next round. Each creature that starts its turn in the cloud must succeed on a DC 13 Constitution saving throw or be blinded until the end of its turn. While blinded in this way, a creature is immobile.
This is excellent, I'll just create it's twin, but not share; that willl be your honer and privilage
Cool!! I love it!