Bragos, the Life-Giver

Amphibious. The dragon can breathe air and water.

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

Telepathic Speech. You can form a telepathic connection between your mind and the mind of another. As a bonus action, choose one creature you can see within 30 feet of you. You and the chosen creature can speak telepathically with each other while the two of you are within a number of miles of each other equal to your Charisma modifier (minimum of 1 mile). To understand each other, you each must speak mentally in a language the other knows.
The telepathic connection lasts for 16 minutes. It ends early if you are incapacitated or die or if you use this ability to form a connection with a different creature.

Slasher. Once per turn when you hit a creature with an attack that deals slashing damage, you can reduce the speed of the target by 10 feet until the start of your next turn. When you score a critical hit that deals slashing damage to a creature, you grievously wound it. Until the start of your next turn, the target has disadvantage on all attack rolls.

Spellcasting. Bragos is a 16th-level spellcaster. His spellcasting ability is Charisma (spell save DC 18, +9 to hit with spell attacks). Bragos has the following sorcerer spells prepared:
Cantrips (at will): Lightning Lure, Mage Hand, Mind Sliver, Shape Water, Thunderclap
1st level (4 slots): Dissonant Whispers, Shield
2nd level (3 slots): Misty Step
3rd level (3 slots): Counterspell, Hunger of Hadar, Lightning Bolt, Sending, Spirit Guardians (illusory Kuo-Toa), Thunder Step, Tongues
4th level (3 slots): Confusion, Control Water, Evard's Black Tentacles, Storm Sphere, Summon Aberration
5th level (2 slots): Dominate Person, Far Step, Synaptic Static, Telekinesis
6th Level (1 slot): Chain Lightning, Mental Prison
7th Level  (1 slot):
8th Level  )1 slot): Abi-Dalzim's Horrid Wilting, Dominate Monster, Power Word Stun

Metamagic. You have 16 sorcery points that you regain when you finish a long rest. You may use them for the following effects:
- Distant Spell: When you cast a spell that has a range of 5 feet or greater, you can spend 1 sorcery point to double the range of the spell. When you cast a spell that has a range of touch, you can spend 1 sorcery point to make the range of the spell 30 feet.
- Quickened Spell: When you cast a spell that has a casting time of 1 action, you can spend 2 sorcery points to change the casting time to 1 bonus action for this casting.
- Transmuted Spell: When you cast a spell that deals a type of damage from the following list, you can spend 1 sorcery point to change that damage type to one of the other listed types: acid, cold, fire, lightning, poison, thunder.

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +16 to hit, reach 15 ft., one target. Hit: 20 (2d10 + 9) piercing damage.

Claw. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 16 (2d6 + 9) slashing damage.

Tail. Melee Weapon Attack: +16 to hit, reach 20 ft., one target. Hit: 18 (2d8 + 9) 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 20 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.

Breath Weapons (Recharge 5–6). The dragon uses one of the following breath weapons.

Lightning Breath. The dragon exhales lightning in a 120-foot line that is 10 feet wide. Each creature in that line must make a DC 23 Dexterity saving throw, taking 88 (16d10) lightning damage on a failed save, or half as much damage on a successful one.

Repulsion Breath. The dragon exhales repulsion energy in a 30-foot cone. Each creature in that area must succeed on a DC 23 Strength saving throw. On a failed save, the creature is pushed 60 feet away from the dragon.

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).

In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

You have one reaction per round, which you may use on any other creature's turn. You may use your reaction to cast Absorb Elements, Shield, or Counterspell, or you may make one melee attack of opportunity when a creature leaves your reach.

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 15 feet of the dragon must succeed on a DC 24 Dexterity saving throw or take 16 (2d6 + 9) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.