Blue eyes ultimate dragon

Legendary Resistance (4/Day, or 5/Day in Lair). If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack. The dragon makes two claw attacks and one tail. It can replace one attack with a use of Spellcasting to cast Shatter (level 3 version).

Claw. Melee Attack Roll: +16, reach 15 ft. Hit: 18 (2d8 + 9) Slashing damage plus 11 (2d10) Lightning damage.

Tail swipe. Melee Attack Roll: The dragon swipes it's tail in a 10ft long semi circle behind it. It does 10d8 bludgining damage to all creatures in the circle.

White lightning: The dragon fires a 90 foot long, five ft wide line on electrical energy any creature in the line makes a DC 18 Dex save or takes 10d12 lightning damage and half as much on a successful save.

Neutron Blast Attack: The dragon fires three 90 ft long five ft wide line of electrical energy any creature in the line makes DC 20 Dex save or takes 30d12 lightning damage and half as much on a successful save. 

Spellcasting. The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 22):

At Will: Detect Magic, Invisibility, Mage Hand, Shatter (level 3 version)
1/Day Each: Scrying, Sending

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, the dragon can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each of its turns.

Cloaked Flight. The dragon uses Spellcasting to cast Invisibility on itself, and it can fly up to half its Fly Speed. The dragon can’t take this action again until the start of its next turn.

Sonic Boom. The dragon uses Spellcasting to cast Shatter (level 3 version). The dragon can’t take this action again until the start of its next turn.

Tail Swipe. The dragon makes one Claw attack.