1. Harry was lucky not to be expelled
2. Attempted to use on infiri
3. The reason George is missing an ear

From the Half Blood Prince ' Blood spurted from Malfoy's face and chest as though he had been slashed with an invisible sword. He staggered backward and collapsed onto the waterlogged floor with a great splash, his wand falling from his limp right hand. Slipping and staggering, Harry got to his feet and plunged toward Malfoy, whose face was now shining scarlet, his white hands scrabbling at his blood-soaked chest.'