If the tarrasque fails a saving throw, it can choose to succeed instead.
3
per day
The tarrasque has advantage on saving throws against spells and other magical effects.
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.
The tarrasque deals double damage to objects and structures.