Burrowing.
The dragon may burrow underground as a bonus action, moving downward or sideways at its full burrow speed.

Magic Resistance.
The dragon has advantage on all saving throws against spells and other magical effects and is immune to the Maze spell.

Sneak attack.
Once per round, one of the dragon's melee attacks may deal +10 (3d6) damage of the first damage type listed in the attack if it has advantage on the attack roll.

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

Multiattack.
The dragon makes one bite attack and two claw attack.

Bite.
Melee Weapon Attack: +13 to hit, reach 15 ft., one target.
Hit: 18 (2d10+7) Piercing damage plus 11 (2d10) Slashing damage.

Claw.
Melee Weapon Attack: +13 to hit, reach 10 ft., one target.
Hit: 14 (2d6+7) Piercing damage plus 7 (2d6) Slashing damage.

Tail.
Melee Weapon Attack: +13 to hit, reach 20 ft., one target.
Hit: 14 (2d6+7) Bludgeoning damage plus 7 (2d6) Slashing damage.

Burrowing Ambush.
The dragon may only use this action if it is burrowing. The dragon surfaces at any point of the map and immediately makes one bite attack and two claw attacks, with advantage on all three attack rolls. Any creature within 10 feet of the dragon must succeed on a DC 22 Dexterity saving throw or be knocked prone from the force of the dragon exiting its burrow and be moved 5 feet away.

Sand Breath (Recharge 5-6).
The dragon exhales scorching sand in a 60-foot cone. Each creature in the area of effect must make a DC 20 Constitution saving throw, taking 38 (11d6) Fire damage plus 38 (11d6) Slashing damage on a failed save, or half as much on a success.

Frightful Presence.
Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 18 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, 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 dragon's Frightful Presence for the next 24  hours.

Sand Wall.
The dragon may raise a dust cloud around itself as a bonus action. Any attack rolls against the dragon are made with disadvantage until the start of its next turn, and all of its melee attacks have advantage until the start of its next turn.

The dragon can take 3 legendary actions, 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.

Hunter's Sense.
The dragon makes a Wisdom (Perception) check, and if a creature is hidden from the dragon, it's not hidden from it anymore.

Fast Burrowing.
The dragon burrows up to its full burrowing speed or, if it was already burrowing, can use its Burrowing Ambush.

Tail Attack.
The dragon makes a tail attack.

Wing Attack (Costs 2 Actions).
Each creature within 20 feet of the dragon must succeed on a DC 22 Strength saving throw or be pushed back 20 feet, take 14 (4d6) Slashing damage, and become blinded until the end of their next turn. A successful save halves the damage and negates the blinded condition. The dragon can then burrow up to half its burrowing speed.