Which spells did the Half-Blood Prince invent?

The Half-Blood Prince did not invent any spells. The Half-Blood Prince was a pseudonym used by Severus Snape in his Potions textbook. The spells in the book were not his inventions, but rather his own unique additions and improvements to existing potions spells.

Here are some of the spells that Snape added to the Potions textbook:

* Sectumsempra: This is a very powerful and dangerous spell that creates a series of deep, bloody wounds that are nearly impossible to heal. It is a powerful, yet incredibly dangerous spell, reflecting Snape's own tormented nature.

* The Unbreakable Vow: This spell was not Snape's invention, but he was known to be an expert in it and used it to bind himself to Narcissa Malfoy, guaranteeing that he would protect Draco Malfoy.

The Half-Blood Prince, while a brilliant Potions student, did not invent any new spells. His contributions to the Potions textbook were his own personal notes and interpretations of existing spells.