Levicorpus

Notes

Levicorpus is quite similar to the Anti-gravity Mist used in the maze during the Tri-Wizard Tournament. Since several teachers contributed to the event (Hagrid the skrewts, Moody the portkey, etc), then it is very possible that the Mist was Snape's invention, since he was the Half-Blood Prince, inventor of Levicorpus (HBP28).

Harry saw Levicorpus performed by the Death Eaters at the Quidditch World Cup, but did not know what spell it was. A year later, he watched his father James perform the spell on Snape a year later, while looking into Snape's memories in the Pensieve (OP28).

Harry found the incantation scribbled in the Half-Blood Prince's potions book and blindly performed it on Ron, turning him upside-down. Later they laughed about it, but Hermione did not see the humor:

"Maybe your dad did use it, Harry," said Hermione, "but he's not the only one. We've seen a whole bunch of people use it, in case you've forgotten. Dangling people in the air. Making them float along, asleep, helpless."

"My dad used this spell," said Harry. "I — Lupin told me."

'This last part was not true; in fact, Harry had seen his father use the spell on Snape, but he had never told Ron and Hermione about that particular excursion into the Pensieve. Now, however, a wonderful possibility occurred to him. Could the Half-Blood Prince possibly be — ?

Harry started to believe that his father James was the Half-Blood Prince, and asked Lupin about the spell.

Remus Lupin sought to reassure Harry that Levicorpus was a common spell back in the day, brushing off any worries by saying "Oh, that one had a great vogue during my time at Hogwarts," and "...it was very popular.... You know how these spells come and go" (HBP16). But Harry didn't believe him; Levicorpus was special and personal to him because he connected the spell to his father James, and had come to believe that James might indeed be the mysterious creative genius who rewrote a textbook. Lupin put that theory to rest because James was a pureblood, and would never call himself "Prince."

So that should have been the end of it. Lupin dismissed Levicorpus as just a fad, a jinx used as a funny joke by all students in all houses. But was Lupin being totally honest with Harry, or was he just being evasive? And how in the world did James learn the spell if he was not the Half-Blood Prince and had ever heard of him? Snape certainly would not have shared with his worst enemy.

There are several ways the Marauders might have gotten a look at the Half-Blood Prince Potions Book and Levicorpus. The most obvious is that Lily Evans was also in Gryffindor, and might have borrowed the book from her then-friend, Severus. In fifth year, everyone was studying for O.W.L. exams and books were everywhere. Glancing into it, Sirius and James might have realized it contained lots of good jinxes and hexes, and without knowing who the Prince was, they might have hidden the book or made it unplottable so no one else could find it. When both Sirius and James were dead, perhaps the book appeared in the Potions classroom again. Snape seemed to hint at a similar conclusion when Harry used another spell from the Prince's book, Sectumsempra, on Draco. Snape insisted on seeing all of Harry's books, asking if he bought them in Diagon Alley, and Harry switched book covers with Ron to try and fool him (HBP24).

It's possible that Snape thought Sirius had given the old book to Harry before his death in order to cause mischief, or that only the heir of the Marauders could find the book, which seems most plausible.

We do have one major clue that James had indeed seen the Half-Blood Prince's written instructions in the book: he used the spell nonverbally, just as the Prince had suggested (OP28, HBP12). In contrast, Hermione had only been told about the spell by Harry and Ron without seeing the instructions, and she whispered the spell aloud at Gringotts (DH26). So it seems clear that somehow James had seen Levicorpus in the Half-Blood Prince book and then used Snape's own spell against him, perhaps unknowingly. And Snape never forgot it, of course.

"You dare use my own spells against me, Potter? It was I who invented them - I, the Half-Blood Prince! And you'd turn my inventions on me, like your filthy father, would you? I don't think so . . . no" (HBP28)

Ironically, we have no canon from memories or in the present with Snape performing Levicorpus, only James, the Death Eaters, Voldemort, Harry, and Hermione (in the Gringotts vault).