Blood Powered. If dealt slashing damage, the next attack deals an extra amount of damage equal to half of slashing damage taken.

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

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

Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 15 (2d10+5) piercing damage plus 9 (2d8) necrotic damage.

Claw. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 9 (1d8+5) slashing damage.

Blood Breath (Recharge 5–6). The dragon vomits acid blood in a 60-foot cone. Each creature in that area must make a DC 24 Constitution saving throw. On a failed save, the creature takes 20 (4d10) acid damage and 10 (2d10) necrotic damage, and it's blinded for one minute or until it takes an action to remove the condition in some way. On a successful save the creature takes half as much damage and isn’t blinded.

Spellcasting (Blood Magic). The dragon casts one of the following spells, requiring no spell components and using Charisma as the spellcasting ability (spell save DC 19). To cast them the dragon must use a Claw Attack on itself (dealing half damage).

2/day each: inflict wounds, stinking cloud, contagion, regenerate

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.

Boiling Blood. The dragon can corrupt a target creature’s blood, dealing 15 (5d6) necrotic damage. The target creature can make a Constitution saving throw (DC 16) to take half damage on a success.

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.

Blood Magic (Costs 2 Actions). The dragon uses Boiling Blood or Spellcasting.

Blood Bomb (Costs 2 Actions). The dragon spits a ball of blood (costing 5 hit dice) that that explodes at a point it can see within 50 feet of it. Each creature within a 20-foot-radius sphere centered on that point must succeed on a DC 20 Dexterity saving throw or take 13 (3d8) necrotic damage and be knocked prone.