Create Undead Dragon

This spell creates an undead dragon that serves under your command. This spell exhausts you both mentally and physically, you can no longer move this turn or take any actions and you skip your next turn, however, you can still command the undead dragon as if it were your turn this turn and next turn. This creature has the same statistics as the ancient dragon who's heart you used to cast this spell. The undead dragon cannot take legendary actions and it becomes resistant to necrotic damage. Additionally, its bite attack and breath weapon also deal necrotic damage rather than its original damage type. The dragon is created in any space you can see that is large enough to fit the undead dragon. If there is no space large enough to fit the dragon the spell fails, the spell slot is wasted, but the material components are not consumed.

On each of your turns, you can use a bonus action to mentally command the dragon you made with this spell. You decide what action the creature will take and where it will move during its next turn, or you can issue a general command, such as to guard a particular chamber or corridor. If you issue no commands, the creature only defends itself against hostile creatures. Once given an order, the creature continues to follow it until its task is complete. The dragon regains all hitpoints after a long rest, during which it must stay still for 8 hours.

The dragon is under your control until the spell ends or until you die. The spell ends when the dragon's hitpoints become zero. Once the dragon's hitpoints become zero, all of the bones and flesh that were created to form the undead dragon's body disintigrate. If you die, you lose control of the dragon and it runs rampant, attacking everything in sight until it dies. If you cast this spell while you have another undead dragon that was summoned by this spell under your command, the old undead dragon disintigrates and is replaced by the new one you created.