Cardiac Arrest

Touch one living creature, giving it intense chest pain and forcing it to make a Constitution saving throw. On a failed save, the creature's maximum hit points are reduced by 10d8 (necrotic) and it is unconscious for 1 minute. After regaining consciousness, the creature cannot regain hit points until it completes a long rest. On a successful saving throw, the creature sustains necrotic damage equal to half the die roll and remains conscious unless this reduces it to 0 hit points. In either case, if the maximum hit point reduction or damage is sufficient to cause instant death, the creature dies.