"Avada Kedavra" is one of the three Unforgivable Curses in the Harry Potter series created by J.K. Rowling. It is known as the Killing Curse, and its incantation causes instant death to the victim without any physical harm. The curse is characterized by a flash of green light and is considered one of the darkest forms of magic. Using "Avada Kedavra" is illegal in the wizarding world, and only a few powerful dark wizards, such as Lord Voldemort, are known to wield it. The curse reflects the moral implications of using magic to take a life, emphasizing the themes of good versus evil in the series.