Adult White Pearl Dragon

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.

Multiattack. The dragon can use its Calming Presence. It then makes three attacks: one with its bite and two with its tail. Or it can use it's Action to Constrict, or use a breathe attack. 

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (2d10 + 3) piercing damage.

Tail. Melee Weapon Attack: +7 to hit, reach 15 ft., one target. Hit: 17 (2d8 + 7) bludgeoning damage.

Constrict. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 23 (6d6 + 2)bludgeoning damage, and the target is grappled (escape DC 16). Until this grapple ends, the creature is restrained, and the dragon can't constrict another target.

Calming Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC18 Wisdom saving throw or become Calmed for 1 minute, and is unable to attack the dragon or be angry or upset at it in any fashion unless the dragon does them harm. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success, or, if the dragon harms them or an ally of their's, the effect is ended instantly. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Calming Presence for the next 24 hours.

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

Moonlit Breath. The dragon releases a beam of moonlight in a 60-foot cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 40 (10d6) Radiant damage on a failed save, or half as much damage on a successful one.

A shapechanger makes its saving throw with disadvantage. If it fails, it also instantly reverts to its original form and can't assume a different form until it leaves the spell's light.

Sleep Breath. The dragon exhales paralyzing gas in a 60-foot cone. Each creature in that area must succeed on a DC 18 Constitution saving throw or fall asleep for 3d6 hours. 

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.

Constrict. The dragon Constricts.

Consume Negative Dreams and Thoughts; Pearl dragons have the unique ability to Consume/be empowered by different things, and convert the energy from that into pearls for their horde. White pearls have the ability to eat bad dreams, self-depreciating thoughts, and traumatic memories. These turn into pearls within the dragon's body, and are later regurgitated to add to the dragon's hoard.