Ancient Crimson Dragon

legendary fortitude. when the dragon dies, it comes back to life at half hit points

tail. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 59 (10d10 + 13) bludgeoning damage.

bite. Melee Weapon Attack: +112 to hit, reach 5 ft., one target. Hit: 71 (8d12 + 16) piercing damage.

claw. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 160 (7d20 + 13) slashing damage.

crimson preservation. the dragon exhales deep red energy in a 90 foot cone. each creature in the area must make a DC 17 constitution saving throw. on a success, the creature is knocked prone, on a failure, the creature begins to become petrified. on its turn, the creature can repeat the saving throw, ending the effect on a success. on the third fail, the creature becomes petrified and dies.

the dragon can take a legendary action at the end of another creatures turn. only one can be used at a time.

tail surprise attack. the dragon makes a tail attack with advantage.