Silence The Earth. A sphere with a one mile radius  is centered on the dragon where Silence is in constant effect.
Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

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 plus 4 (1d8) cold damage.
Claw. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage.
Tail. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 6) bludgeoning damage.
Cast Greater Invisibility. The dragon can cast Greater Invisibility  at will, making an attack will end the effect. 
Displacement Breath (Recharge 5–6). The dragon exhales a colorless force in a 5 by 30 ft line. The force can be seen by how it hits the environment (dust kicks up, objects might be pushed etc.) Each creature in that area must make a DC 19 Constitution saving throw, on a failed save, the creature is teleported to a random plane of existence, roll a d20 to determine the location. Any creature teleported remains in the new realm for a turn unless held there longer by other means.

1) Elysium

2) Beastlands

3) Arborea

4) Ysgard

5) Limbo

6) Pandemonium

7) Abyss

8)  Carceri

9) Gray Waste

10) Gehenna

11) Baator

12) Acheron

13) Mechanus

14) Arcadia 

15) Mount Celestia

16) Bytopia

17) Elemental Plane of Earth

18) Elemental Plane of Fire

19) Elemental Plane of Wind

20) Elemental Plane of water

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 19 Dexterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.