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

Innate Spellcasting (Psionics). The adult crystal dragon's innate spellcasting ability is Intelligence (DC 14). The adult crystal dragon can innately cast the following spells, requiring no material components:

At will: charm person, plane shift

Multi attack. The adult crystal dragon uses its frightful prescience then makes a bite attack and two claw attacks. 

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 10 (2d8 + 2) piercing damage. 

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 6 (2d4 + 2) slashing damage. 

Tail. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 8 (2d6 + 2) 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.

Light flare breath (Recharges 5/6). The crystal dragon exhales an orb of immense light that is 5ft by 5ft which lands in a place they can see within 30ft. Any creature within the orb's lands must make a DC 13 Constitution saving throw or take 42 (14d6) radiant damage and are blinded for 1d10 minutes. Any creature within 30ft of the orb must make a DC 13 Dexterity saving throw or have disadvantage on all attack rolls for the next 1d4 minutes. Creatures who are sensitive to sun light or light in general made the save with disadvantage.  

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 (Costs 1 Action). The dragon makes a Wisdom (Perception) check.

Tail Attack (Costs 1 Action). The dragon makes a tail attack.

Teleport (Costs 1 Actions). The crystal dragon teleports up to 30ft to a place that they can see that isn't currently occupied.