There are two main concerns with this plan. The first is that Brian will be in a highly dangerous situation if Quirrell didn't intend to reveal to him about the Dark Lord. He is not the opponent of Quirrell no matter how many spells he has mastered. He is just a first-year wizard after all.
Fortunately, Brian had something to depend on. He looked down at the ring hanging around his neck. This was gifted to him by his mother before he came to Hogwarts. It is a powerful magical item enchanted with the Protego Maxima spell, a stronger version of the Shield Charm.
It would last for quite a while until the professors came to his rescue. Though he had no doubt that Voldemort must have noticed the powerful artefact on him. That's probably why Quirrell changed his mind.
Coupled with the fact that Voldemort doesn't want to expose himself at the moment, the likelihood of Brian being in danger is very low. Then, after hearing that he was from the Fawley family, knowing their close relationship with the Lestranges - one of Voldemort's faithful followers - Brian was pretty sure that the Dark Lord would want to recruit him into one of his minions.
The second danger lies in Voldemort's Legilimency. Even though he is in a weakened state now, the Dark Lord is still not to be trifled with.
In the original plot, Voldemort had seen through Harry lies when he asked him if he obtained the Philosopher's stone from the Mirror of Erised. Clearly, he had used Legilimency on Harry.
Brian was not willing to take risks, so before meeting Quirrell, he had spent his measly points to increase his Occlumency skill by one rank. Fortunately, it was enough to evade Voldemort's probe.
In the end, it all worked out. Brian was able to gain the trust of Voldemort. Now all he had to do was play the part of the Dark Lord's loyal servant.
XXX
In the Great Hall, Draco could be seen laughing at Harry and Ron at the Gryffindor's table.
"Poor Weasley and Potter. I've heard you went looking for the trolls last night, but were caught by the professors?" Draco mocked, followed by jeers from Crabbe and Goyle.
"You should thank the professors for stopping you; otherwise, you would have ended yourself in the troll's stomach."
"Shut up, Malfoy!" With a face as red as his hair, Ron roared angrily. Harry remained silent throughout this time because he was too ashamed to show his face.
"Hahaha!" However, Draco brushed him off and sauntered out of the hall with his thugs, laughing the entire time. The rest of the students were laughing, too.
"Damn, Malfoy. I swear I'm going to punch that face someday." Ron sat back down and whispered to Harry.
Last night, the two of them were worried about Hermione after not seeing her at the feast. When Professor Quirrell arrived to tell that a troll had broken into the school, they quickly went to look for her.
After hearing from Parvati Patil that Hermione was last seen in the toilet crying, they quickly rushed over there only to find a sleeping troll in front of the girl's toilet. Not long after that, they were spotted by the professors who were searching for the troll.
When they caught sight of Professor McGonagall's angry-looking figure, they were so terrified they were shaking. They were frozen in place by her sharp gaze, not daring to take even a small step.
After examining the troll, Professor Snape remarked that someone had brought it down with the Draught of Living Death. He then scoffed at the two first-year Gryffindors.
"Clever move, but Potter and Weasley obviously couldn't have pulled it off."
The furious Professor McGonagall shouted in a shaking voice, "Do you know how dangerous trolls are? Five points from Gryffindor for each of you. Now go back to your dorm!"
In panic, the two Gryffindors returned to the common room, where they found Hermione sitting near the fireplace with a book in her hand.
"Where have you been? Don't you know there's a troll in the school?" Hermione put down her book and looked up at them.
"There you are Hermione! We thought you were still in the girl's bathroom. We were looking for you," Ron told her.
"So... you guys were looking for me?" Hermione asked, standing up. "Do you know how dangerous that was?"
"Wait. Did you get caught by the professors?"
"Uhh…"
"You were caught, weren't you? Let me go and explain to them."
Just before Hermione could leave the common room, Harry and Ron quickly stopped her.
"It's useless, Hermione. Trust me, Snape will find excuses to deduct points from you even if you told them we were looking for you," Harry said.
"By the way, how did you defeat the troll?" Ron asked curiously. "Snape said that someone used a sleeping potion on the troll."
"It wasn't me. It was Brian," Hermione answered, much to their shock.
"What? You said it was Fawley?" Ron's eyes widened.
"Yes, he saved me." Hermione nodded.
"Impossible! You're lying!" Ron shouted in disbelief before being quickly silenced by her glare.
"I'm not! It was Brian who saved me."
"That's weird… It was almost as if he knew the troll was going to be there," Harry said thoughtfully. "And why would he carry a sleeping potion with him?"
"Harry, do you think it was Bryan who released the troll?" Hermione turned to the raven-haired boy. "Forget it. I'm done talking with you all. I'm going to sleep. Good night!"
Turning around, Hermione left the two dumbfounded Gryffindors behind as she climbed the stairs to her dorm.
After Draco had left, Harry and Ron continued to talk about what happened last night.
"I think there's something wrong with Fawley. His appearance last night is too coincidental," Harry told Ron.
Ron stuffed the sandwich into his mouth and mumbled, "He must have heard Professor Quirrell's yelling and ran off to fight the troll."
"He probably wants to show off," he finished with distaste.
"That's the problem!" Harry said quietly, glancing at Brian who was eating breakfast quietly from a distance. "He never mentions it to anyone else. Only a few people know that he has defeated that troll."
"And do you remember the time when he led us to the forbidden corridor? He must have done it on purpose!"
"But why would he do that?" Ran asked.
"Maybe he wants to get the treasure hidden inside that door," Harry guessed.
"We're late for class, Harry. Hurry up and finish your food," Ron said, stuffing the last bite of the sandwich into his mouth.
XXX
After the DADA class, Brian stayed behind to talk with Professor Quirrell.
"Sorry for causing trouble to you last night, Professor Quirrell," Brian said apologetically.
"It's fine. I've got the information I want," Quirrell waved it off. "Snape did a good job of testing that Cerberus for me."
"Then what can I do to help?" Brian asked, his voice sounding a little excited.
"Ah yes. Can I entrust you to find a way to get past that Cerberus?" Quirrell mused. "That big dog had to be Hagrid's. You can try to get some information from him."
"Sure," Brian nodded and exited the classroom.
Some time had passed since the troll incident. Brian set aside the task Quirrell had given him and returned to his studies. He had finished his first-year Transfiguration courses and was now focusing on the second-year.
He was a little slow in Charms but that mostly had to do with his wand movement work. His wand is still rejecting him, which is becoming a hassle. Though he still did manage to finish this year's courses.
The same applies to Potions. Finally, he was no longer a troll.
[Skill]
Transfiguration - Troll → Junior Wizard
Charms - Troll → Junior Wizard
Potions - Troll → Junior Wizard
(Congratulations! You're no longer a stupid wizard!)
As for other subjects… Unfortunately, he just didn't have the time or energy, so he had to put them off for the time being. His points had also gone up a little, which he got from watching a few Quidditch matches and soon there would be another Quidditch match between the Slytherin and Gryffindor.