Adult Titanium Dragon

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

Dragons Light (Recharge 5). The dragon exhales a beam of blinding light in a 200 foot line that is 10 feet wide. Each creature in that line must make a DC 19 Dexterity saving throw, taking 66 (12d10) Radiant damage on a failed save, or half as much damage on a successful one.

Multi-attack. The dragon makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 7) piercing damage plus 5 (1d10) radiant damage.

Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) slashing damage.

Tail. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 16 (2d8 + 7) bludgeoning damage.

Volley of Light (Recharge 5). The dragon casts bright light in a 20 foot radius circle from any point it can see. It begins raining radiant bolts that deal. 12 (4d4+4) radiant damage if a creature starts and/or ends their turn within the circle. this effect lasts for 3 rounds.

Opportunity attack. This creature can make a "claw", "bite" or "tail" attack if another creature moves more than 5 ft away from this creature.

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 spreads its wings wide releasing light below. Each creature within 10 feet of the dragon must succeed on a DC 20 Dexterity saving throw or take 14 (2d6 + 7) Radiant damage and be knocked Prone. The dragon can then fly up to half its flying speed.