You must make skin to skin contact with your target, scales do not count, and the spell will not cast. They must be healthy, or the spell will kill them. If they are a young child or an elder, they might also be too weak to survive the spell.

After 30 minutes of the spell being cast, if the target has not been healed by something (magic, consumable, etc.), not including rests, they instantly go to 0 HP. After 5 minutes if they have not been saved, they become zombified. They gain full health (as much health as they can get with the zombified condition) and lose all conditions other than zombified.