Amphibious. The dragon can breathe both air and water.

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

Regeneration. The Dragon regains 20 hit points at the start of its turn if it has at least 1 hit point and isn’t in sunlight or running water. If the dragon takes radiant damage or damage from holy water, this trait doesn’t function at the start of the dragon’s next turn.

Spider Climb. The dragon can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Dragon Weaknesses. The dragon has the following flaws:

Forbiddance. The dragon can’t enter a residence without an invitation from one of the occupants.

Harmed by Running Water. The dragon takes 20 acid damage if it ends its turn in running water.

Stake to the Heart. If a piercing weapon made of wood is driven into the dragon’s heart while the dragon is incapacitated in its resting place, the dragon is paralyzed until the stake is removed.

Sunlight Hypersensitivity. The dragon takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

Multiattack. The dragon makes one Bite attack and two Claw attacks.

Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 15 (2d10 + 4) piercing damage plus 3 (1d6) necrotic damage.

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage.

Blood Breath (Recharge 5–6). The dragon exhales reddish necrotic energy in a 60-foot cone. Each creature in that area must make a DC 17 Constitution saving throw. On a failed save, the creature takes 35 (10d6) necrotic damage and the target’s hit point maximum is reduced by an amount equal to the necrotic damage taken, and the dragon regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0. A humanoid slain in this way and then buried in the ground rises the following night as a vampire spawn under the dragon’s control.

Charm. The dragon targets one humanoid it can see within 30 feet of it. If the target can see the dragon, the target must succeed on a DC 17 Wisdom saving throw against this magic or be charmed by the dragon. The charmed target regards the dragon as a trusted friend to be heeded and protected. Although the target isn’t under the dragon’s control, it takes the dragon's requests or actions in the most favorable way it can, and it is a willing target for the dragon’s bite attack.

Each time the dragon or the dragon’s companions do anything harmful to the target, it can repeat the saving throw, ending the effect on itself on a success. Otherwise, the effect lasts 24 hours or until the dragon is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.

Children of the Night (1/Day). The dragon magically calls 2d4 swarms of bats or rats, provided that the sun isn’t up. While outdoors, the dragon can call 3d6 wolves instead. The called creatures arrive in 1d4 rounds, acting as allies of the dragon and obeying its spoken commands. The beasts remain for 1 hour, until the dragone dies, or until the dragon dismisses them as a bonus action.

Change Shape. The dragon magically transforms into any creature that is Medium or Small, while retaining its game statistics (other than its size). This transformation ends if the dragon is reduced to 0 hit points or uses a bonus action to end it.

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.

Claw. The dragon makes one Claw attack.

Bloody Rebirth (Costs 3 Actions). The dragon targets a creature or an object not being worn or carried that it can see within 60 feet of it. The target must succeed on a DC 17 Constitution saving throw or take 28 (8d6) necrotic damage. If this damage reduces the target to 0 hit points, the target rises as a vampire spawn.