Reasons, Part One
Love has a powerful magic, Riddle knows this very well, after all, his greatest threat Albus Dumbledore, preaches this kind of thing all day long.
However, this power is very limited and passive.
It is the strength that sheep use to defeat lions, but why should a lion like myself learn from sheep?
Lions that try to learn from sheep will only dull their claws and be threatened by jackals.
Dumbledore was the lion whose claws were being sharpened. In his student days, Dumbledore, who was already a top wizard, was entangled by the Ministry of Magic, which was composed of weaklings.
If Horace Slughorn taught Riddle the importance of spreading his ideas, then Dumbledore is a perfect counterexample.
"Tom, you certainly know a lot about Gormlaith Gaunt's downfall, but you don't know the real inside story."
"The room where this story took place, the room of Isolt's twin daughters, remains intact and is the best place for the Britain Ministry of Magic and the America Ministry of Magic to study the power of love."
"The twin daughters of Chadwick and Isolt, who would not have died otherwise, sacrificed themselves for their mother. This triggered the power of love, and that is the real reason for Gormlaith's defeat."
"After all, while Pukwudgie is powerful, he's not powerful enough to kill Gormlaith," Dumbledore explained.
"Then the part of my soul that occupied my physical body was also taken by the so-called Ministry of Magic to study the place where his physical form collapsed, because of Lily Potter's love?" Riddle frowned.
"No, the power of love you face far surpasses that of Gormlaith, and Lily's love isn't like the one in the story I told before, lingering in a room. Instead, it's deeply etched into her child Harry. That's why you suffered another defeat this June."
"The power that resides within Harry is an unparalleled miracle. He can even instinctively use love as his weapon against others, instead of waiting to retaliate when he is hurt by them," Dumbledore said with a wistful look in his eyes.
He began to recall Harry's incredible Red Spark charm in the Defense Against the Dark Arts room, and the Phoenix born in the innermost room of the Forbidden Lands.
"This goes beyond the existing realm of magic." Riddle said with even greater interest than before, and then couldn't help but mutter Harry's name.
"Okay, where's my room? I need to go prepare my lesson plans!"
"I can't wait to meet that miracle boy," Riddle said swiftly after regaining his composure.
"Go to the Defence Against the Dark Arts Professor's office on the fourth floor later. I don't think I've had a frank conversation with you yet, and my predecessors are waiting for my explanation." Dumbledore waved his wand.
A dirty wine bottle and two glasses appeared in the air. The bottle automatically tilted itself and filled each glass with a honey-yellow liquid, then the glasses floated towards the two people in the room.
"Madam Rosmerta's finest Oak-matured mead, you can sip as you listen," Dumbledore said, raising his glass to Riddle. Riddle took his own glass and sipped.
Riddle seemed to really like it; the delicious liquid smoothed out his furrowed brow. "Madam Rosmerta? Never heard of it."
"But I'm still a seventeen-year-old kid, how can I drink alcohol?" Riddle said sarcastically while taking a few sips himself. He cherished the feeling of having a physical body to enjoy delicious food.
"I almost forgot that your birthday is December 31st, so you could say you're seventeen."
"Tom, I thought you hated Muggle. In the Wizarding World, a young wizard is seventeen when he comes of age, not eighteen in the Muggle World," Dumbledore retorted. Riddle pursed his lips and took another sip.
After he finished drinking, the bottle in the cup flew over automatically and refilled Riddle.
"Madam Rosmerta was the mistress of the Three Broomsticks and only began to appear in public in 1970."
"At that time you were already in your forties, had long since left Hogwarts, and were living abroad, not yet officially back in Britain."
"Alright, let's get down to business."
"There are three main reasons why I made you the Defense Against the Dark Arts professor," Dumbledore emphasized finally. Riddle's frivolous smile vanished, replaced by a serious expression. The headmasters in the surrounding picture frames also perked up their ears.
"First, the curse of Defense Against the Dark Arts. This curse is caused by the access you gained in the Chamber of Secrets. It is part of Hogwarts and will only disappear if we move to a different location and stop using the name Hogwarts."
"Of course we wouldn't do that. In fact, if the teacher of this course were just a little careful, and we adopted our current method of changing a teacher every year, the worst outcome would be a few months in St. Mungo's Hospital. We usually book several months of treatment for the Defense Against the Dark Arts teacher at St. Mungo's's in advance. Quirrell was just too careless before; he had been hanging out with the most dangerous Dark Wizard all along. When people are unlucky, they will naturally suffer misfortune."
"Some might wonder why we don't just change the name of this course, something like Protective Protection. But that's pointless. This curse is alive in a sense; it doesn't possess Wisdom in the conventional sense, but it can discern these things."
"Seriously speaking, there is only one way to break this curse, and that is to make Tom Riddle the Defense Against the Dark Arts teacher."
"After all, this curse was placed because you failed in your job application. You cursed anyone but yourself to become the professor of this course. That's why Quirrell, who has Tom himself in the back of his head, is affected by the curse. In the eyes of the curse, Quirrell is a separate individual, and also someone who is unworthy to be the professor of this course."
"And when you become the Defence Against the Dark Arts Professor next school year, this curse will no longer be in effect," Dumbledore explained.
"Just for this? Slytherin privileges are being used for pranks?" Phineas Nigellus Black Family, the headmaster of Slytherin House, frowned.
"Headmaster Black, that authority only works when I am a member of Hogwarts, and it's useless when I've been repeatedly refused entry back to Hogwarts."
"Its power is also limited. I cannot curse other professors or even Dumbledore without cause. I can only use it on myself."
"And I cursed Defense Against the Dark Arts because I failed to get a job," Riddle waved his hand, taking a few more sips of mead. "But, just because of that, you think I'm independent?"
"Dumbledore, you are a man of high moral character, and you would never use any unjust means to prolong your life."
"And I am immortal."