Sectumsempra is a dark curse that causes deep and never-healing cuts on the victims body. It is a spell that was invented by Severus Snape, and it is not widely known or used. The spell is recorded in Advanced Potion-Making in Harry Potter. When used to attack a foe, it causes great damage to the person, and their chest, hands, and feet spurt out blood. In the book Harry Potter and the Half-Blood Prince, Snape used the spell on his foe, leaving him scarred and injured. The spell is not an unforgivable curse, but it is considered illicit and sinister. The reason why it is not an unforgivable curse is that it is Snapes personal curse that he created, and it is not widely known or used. The spell is dangerous, and if nothing is done, it can cause severe hemorrhaging. Snape was able to partially heal Draco with an unnamed spell after using Sectumsempra on him.