Chaososaurus

Keen Smell. The Chaososaurus has advantage on
Wisdom (Perception) checks that rely on smell.

Thermal Adaptability. Chaososaurus can modify its body temperature. 

Camouflage. Chaososaurus is invisible when hidden and motionless.

Legendary Resistances (3/Day). If the Chaososaurus fails a saving throw OR a roll to hit, it can choose to succeed to instead.

Enhanced Self Resurrection. If the Chaososaurus reaches 0 HP, it will regenerate to double its previous full HP before it died, will do damage times the amount of times it has lived for every attack (second life is double damage, third life is triple, etc…), and gains back its Legendary Resistances. This Special Trait cannot be used if eaten by another creature.

Light Attraction. If there is a point of bright light within vision of the Chaososaurus, it will focus on that light and attempt to attack it on its next turn unless it is attacked first. An example of this is a flare, torch, or flashlight. 

Multiattack. The Chaososaurus uses roar and makes two claw attacks or one claw and one bite attack.

Bite. Melee Attack: +13 to hit, reach 10 ft., one
target. (4d12 + 8) piercing damage.

Claw. Melee Attack: +13 to hit, reach 10 ft., one
target. (3d8 + 8) slashing damage.

Tail Whip. Melee Attack: +13 to hit, reach 10 ft.,
multiple targets. (2d10 + 8) bludgeoning
damage.

Acid Spit (Recharge 5-6). The Chaososaurus spits acid in a line that is 40 feet long and 5 feet wide. Each creature in that line must make a DC 18 Dexterity saving throw. On a failed save, a creature takes (6d6) acid damage and is blinded. On a successful save, a creature takes half as much damage and isn't blinded. 

Head swipe. Melee Attack: +13 to hit, reach 5 ft., one target. (5d8+6) Bludgeoning damage. If the target is Medium or smaller, it will be knocked back 40 ft from Chaososaurus.

Roar. All creatures within 120ft of the Chaososaurus must succeed a DC 18 Wisdom Saving throw or be frightened for 1 minute. Effects don't stack.

No Bonus Actions.

Opportunity Attack. When a hostile creature moves out of your reach, you can use your reaction to make one melee attack against the creature. The attack occurs just before the creature leaves your reach. 

No Legendary Actions.

No Mythic Actions.