“‘Sirius, I…I think I’m going mad….Back in Dumbledore’s office, just before we took the Portkey…for a couple of seconds there I thought I was a snake, I FELT like one-my scar really hurt when I was looking at Dumbledore-Sirius, I wanted to attack him-‘
He could only see a sliver of Sirius’s face; the rest was in darkness.
‘It must have been the aftermath of the vision that’s all,’ said Sirius, ‘You were still thinking of the dream or whatever it was and-‘
‘It wasn’t like that,’ said Harry, shaking his head. ‘It was like something rose up inside of me, like there’s a SNAKE inside me-‘”
J.K. Rowling “Harry Potter and the Order of the Phoenix”