Ancient Cloud Diver

Keen Senses. The cloud diver has advantage on Wisdom (Perception) checks that rely on sight, hearing, or smell.

Magic Resistance. The cloud diver has advantage on saving throws against spells and other magical effects.

Telepathy. Using telepathy, the cloud diver can magically communicate words, ideas, images, sounds, emotions, and other sensory messages with any creature within 100 feet of it that can understand a language. It can also use it's telepathy to speak with animals.

Shapechanger. Twice per long rest:  The dragon magically polymorphs into a creature that has a challenge rating no higher than its own, or back into its true form. It will automatically revert to it's true form, if it drops to 0 hit points or dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).

In the new form, the dragon retains its alignment, telepathy, proficiencies, 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.

Multiattack. The dragon makes two attacks: one with its bite and one with its claws.

Bite. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 16 (3d6 + 5) piercing damage.

Elemental Claws (Ice). Melee Weapon Attack: +8 to hit, reach 10 ft., one creature. Hit: 22 (3d8 + 6) slashing and (1d4 + 1) cold damage, and the target must succeed on a DC 16 Constitution saving throw or become frozen for 1d6 minutes, or until thawed.