Immutable Form The dragon is immune to any spell or effect that would alter its form. 

Legendary Resistance (3/day) If the dragon fails a saving throw it can choose to succeed instead

Self Destruct When the dragon is reduced to 0 hit points, it explodes, and each creature within 30 feet of it must make a DC 18 Dexterity saving throw, taking 21 (6d6) fire damage and 21 (6d6) piercing damage on a failed save, or half as much damage on a successful one. 

Multiattack The dragon makes three attacks: one with its bite and two with its claws. 

Bite Melee Weapon Attack +11 to hit, reach 10 ft, one target. Hit: 17 (2d10 + 6) piercing damage. 

Claw Melee Weapon Attack: +11 to hit, reach 5ft, one target. HIt: 13 (2d6 + 6) bludgeoning damage. 

Tail Melee Weapon Attack: +11 to hit, reach 5ft, one target. Hit: 15 (2d8 + 6) bludgeoning damage. 

Breath Weapons (Recharge 5-6) The dragon uses one of the following breath weapons. 

Fire Tar Breath. The dragon sprays flaming tar in a 30-foot-cone. Each creature in that area must make a DC 18 Dexterity saving throw, taking 35 (10d6) fire damage on a failed save, or half as much damage on a successful one. On a failed save, a creature is restrained (escape DC 18). While restrained in this way, a creature takes 10 (3d6) fire damage at the start of each of its turns. 

Knockout Gas Breath. The dragon exhales knockout gas in a 60-foot cone. Each creature in that area must succeed on a DC 18 Constitution saving throw or fall unconscious for 10 minutes. This effect ends for a creature if the creature takes damage or someone uses an action to wake it. 

Reaction Name. Enter the description for your action.

The dragon can take 3 legendary action, 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 dragon regains spent legendary actions at the start of its turn. 

Detect. The dragon makes a Wisdom (Perception) check. 

Tail Attack. The dragon makes a tail attack. 

Wing Attack (Costs 2 Actions) The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 19 Decterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.