Black Weredragon

Shapechanger. The weredragon can use its action to polymorph into a Large dragon-humanoid hybrid or into a Young Black Dragon, or back into its true form, which is humanoid. Its statistics, other than its size and AC, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Keen Smell. The weredragon has advantage on Wisdom (Perception) checks that rely on smell.

Amphibious. The weredragon can breathe both air and water while in dragon or hybrid form.

Multiattack. In dragon form, the weredragon makes two claw attacks and one bite or tail attack. In humanoid form, it makes two unarmed or weapon attacks. In hybrid form, it can attack like a dragon or a humanoid.

Bite (Dragon or Hybrid Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) piercing damage plus 4 (1d8) acid damage. If the target is a humanoid, it must succeed on a DC 14 Constitution saving throw or be cursed with werebear lycanthropy.

Claw (Dragon or Hybrid Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Tail (Dragon or Hybrid Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 10 (1d12 + 4) bludgeoning damage.

Acid Breath (Recharge 5 - 6) (Dragon or Hybrid Form Only). The weredragon exhales acid in a 30-foot line that is 5 feet wide. Each creature in that line must make a DC 15 Dexterity saving throw, taking 44 (10d8) acid damage on a failed save, or half as much damage on a successful one