Sand Camouflage. The dragon has advantage on Dexterity (Stealth) checks while in a sandy area and while light or stronger wind is blowing.

Lesser Deathtouch (1/Day). Whenever the dragon hits a creature with a weapon attack that deals damage, it can choose to deal no damage and instead deal damage to the creature's hit point maximum equal to half the amount of the total damage dealt by the weapon attack.

Legendary Resistance (2/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 15 (3d6 + 5) piercing damage plus 3 (1d6) acid or poison damage (dragon's choice).

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 11 (1d12 + 5) slashing damage.

Tail. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 12 (2d6 + 5) bludgeoning damage.

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 13 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.

Acid Breath (Recharge 5–6). The dragon exhales a forceful ray of acid in a 60-foot line that is 15 feet wide. Each creature in that area must make a DC 17 Dexterity saving throw, taking 38 (11d6) acid damage on a failed save, or half as much damage on a successful one.

Change Shape. The dragon magically polymorphs into a humanoid, beast, or monstrosity that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).   In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features of that form.

Megamorph (Recharges after Short or Long Rest). After using its Change Shape, if the dragon reverts back to its true form willingly while using this action, the dragon gains the following benefits for 1 minute:

• 2d12 temporary hit points.
• A +1 bonus to attack rolls to hit and to damage dealt by those attacks.
• +1 bonus to Armor Class.

Spellcasting. The dragon casts one of the following spells, requiring no material components and using Charisma as the spellcasting ability (spell save DC 16, +8 to hit with spell attacks):

1/day each: eldritch blast, fog cloud, create or destroy water, blindness/deafness

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.

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 17 Dexterity saving throw or take 11 (1d12 + 5) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.