Ancent Golden Beryl-dragon

legendary resistance (3/day).  If the dragon fails a saving throw, it can choose to succeed instead

Innate Spellcasting.  the dragons innate spellcasting is int. (spell save DC 22, +14 to hit with spell attacks) they can cast the following spells, requiring no material components 
    At will: shocking gasp, thunderclap, lighting lure, dancing light
  5/day: thunderwave, Witch bolt, Thunderous smite, fog cloud, protection from good and evil
  4/day: healing spirit,gust of wind, calm emotions, enlarge/reduce
  3/day: thunder step , tiny servant , call lighting
 2/day: storm sphere,  polymorph
 1/day: dominate person

Multiattack.  The dragon can use its frightful presence. It then makes 3 attacks one with it bite and two with it claws

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft, one target. hit  10(2d8+1) piercing damage

claw. Melee Weapon Attack: +7 to hit, reach 5 ft, one target hit 8(2d6+1) slashing damage

Tail.  Melee Weapon Attack :+7 to hit, reach 5 ft, one target hit 8(2d6+1) bludgeoning damage

Frightful Presence. Each creature of the dragon's choice that is with in 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 it 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 

lighting breath(5-6)  the dragon exhales lighting in a 80 ft cone . Each creature in it most make a dc 11 dexterity saving throw, taking 67 (15d8) lighting damage on a failed save or half as much on a successful one

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 regain 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 15 dexterity saving throw or take 8 (2d6+1) bludgeoning damage and be knocked prone. the dragon can then fly up to half its speed.