Deadly Snake, Silent Dragon.

Who's the Monster ?

They stepped off the stone staircase at the top, and Professor McGonagall rapped on the door. It opened silently and they entered. Professor McGonagall told Harry to wait and left him there, alone, oblivious to him that Angelina was close behind him.

She noticed him looking around the office with amazement, his attention drifted to the Sorting Hat.
She saw his mixed emotions on his face.

He walked quietly around the desk, lifted the hat from its shelf, and lowered it slowly onto his head. It was much too large and slipped down over his eyes, he looked at it until it spoke.

"Bee in your bonnet, Harry Potter?"

"Er, yes," Harry muttered. "Er-sorry to bother you-I wanted to ask-"

"You've been wondering whether I put you in the right House," said the hat smartly. "Yes... you were particularly difficult to place. But I stand by what I said before"-"you would have done well in Slytherin-"

So Harry must have Slytherin blood.
Or simply her dad did something to him that night.

He grabbed the point of the hat and pulled it off. It hung limply in his hand, grubby and faded. Harry pushed it back onto its shelf, feeling sick.

"You're wrong,"

Ivy turned when she saw a certain decrepit looking bird that resembled a half plucked turkey looking at her.
Animals can feel an invisible person.
then bird burst into flames.

Ivy yelled but thankfully Harry's yell was louder.
He looked feverishly around, but not long later, there was ash in the place of the bird.

The office door opened. Dumbledore came in, looking very somber.

"Professor," Harry gasped. "Your bird-I couldn't do anything-he just caught fire-"

Dumbledore smiled, Ivy moved a bit away, like in a hiding area, even though she was invisible, her standing in the middle of the room would only risk someone knocking into her and getting caught.

"About time, too," he said. "He's been looking dreadful for days; I've been telling him to get a move on." He chuckled at the stunned look on Harry's face.

"Fawkes is a phoenix, Harry. Phoenixes burst into flame when it is time for them to die and are reborn from the ashes. Watch him..."

Ivy looked down as well, a small bird stood out of the ashes.

It's a shame you had to see him on a Burning Day," said Dumbledore, seating himself behind his desk. "He's really very handsome most of the time, wonderful red and gold plumage. Fascinating creatures, phoenixes. They can carry immensely heavy loads, their tears have healing powers, and they make highly faithful pets."

Before Dumbledore could speak another word, however, the door of the office flew open with an almighty bang and Hagrid burst in, a wild look in his eyes, his balaclava perched on top of his shaggy black head and the dead rooster still swinging from his hand.
Oh boy, I thought.

"It wasn' Harry, Professor Dumbledore!" said Hagrid urgently. "I was talkin' ter him seconds before that kid was found, he never had time, sir-"

Dumbledore tried to say something, but Hagrid went ranting on, waving the rooster around in his agitation, sending feathers everywhere.

"it can't've bin him, I'll swear it in front o' the Ministry o' Magic if I have to-"

"Hagrid, I-"

"-yeh've got the wrong boy, sir, I know Harry never-"

"Hagrid!" said Dumbledore loudly. "I do not think that Harry attacked those people."

Ivy looked back at Dumbledore.