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.

Actions

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.

Legendary Actions

The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action 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.

Lair Actions

On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects:

The dragon creates fog as though it had cast the fog cloud spell. The fog lasts until initiative count 20 on the next round.
A thunderclap originates at a point the dragon can see within 120 feet of it. Each creature within a 20-foot radius centered on that point must make a DC 15 Constitution saving throw or take 5 (1d10) thunder damage and be deafened until the end of its next turn.

Additional Lair Actions[–]

At your discretion, a legendary (adult or ancient) bronze dragon can use one or more of the following additional lair actions while in its lair:

Ocean's Call. The dragon conjures a swarm of spectral dolphins. Each creature in the water within 120 feet of the dragon must succeed on a DC 15 Dexterity saving throw or take 5 (1d10) slashing damage; then the swarm vanishes.
Salt Burst. The dragon chooses a point it can see in the lair. The air in a 20-foot-radius sphere centered on that point bursts with abrasive salt crystals. Each creature in that area must succeed on a DC 15 Dexterity saving throw or take 10 (3d6) slashing damage.
Whelming Water. The dragon causes a strong current to course through the water in its lair. The dragon chooses any number of creatures it can see that are standing or swimming in water within 120 feet of it. Each chosen creature must succeed on a DC 15 Strength saving throw or be knocked prone.

Regional Effects

The region containing a legendary bronze dragon's lair is warped by the dragon's magic.

Once per day, the dragon can alter the weather in a 6-mile radius centered on its lair. The dragon doesn't need to be outdoors; otherwise the effect is identical to the control weather spell.
Underwater plants within 6 miles of the dragon's lair take on dazzlingly brilliant hues.
Within its lair, the dragon can set illusory sounds, such as soft music and strange echoes, so that they can be heard in various parts of the lair.

If the dragon dies, changed weather reverts to normal, as described in the spell, and the other effects fade in 1d10 days.

Additional Regional Effects[–]

Any of these effects might appear in the area around a bronze dragon's lair, in addition to or instead of the effects described in the Monster Manual:

Phantom Escort. Ghostly naval ships from an ancient armada appear, escorting well-meaning creatures in need of the dragon's help toward the dragon's lair.
Underwater Pursuit. Sailors glimpse the shadowy, illusory form of a dragon in the depths below them, keeping pace with their vessel.
Unfailing Faithfulness. Sapient creatures that spend a year within 10 miles of the dragon's lair find it nearly impossible to break a promise.

Ancient Bronze Dragon