I own nothing you may recognize.
Forgive my poor quality in writing of these events in first year. Honestly most of Harry's non-adventure story is hard to write so bear with me, as I write changes and struggle through the other stuff.
October 31, 1991, Great Hall, Halloween Feast
"Troll, Troll in the dungeon, just thought you should know," Professor Quirrell said as he rushed into the Hall, causing everyone to start panicking, as he passed out falling forward.
"ATTENTION!" Professor Dumbledore said after amplifying his voice with a charm, causing everyone to fall silent.
"Headmaster, if what Professor Quirrell said is true, then we need to get the children to safety," Professor McGonagall said simply.
"Indeed, Professor McGonagall, which is why I need all Prefects to lead your housemates to your common rooms, where the feast will continue. Professors Vector, and Sinestra please go with the Hufflepuffs to make sure they get to their common room safely, Professor Babblings, can you and our two head students escort the Slytherins to their Common room and then remain with them. Now go," Professor Dumbledore said and once he had gotten nods from everyone, he dismissed them.
"Hadrian, Hadrian, I need your help," Neville said as their two houses headed to the grand staircase.
"What's up Neville?" Hadrian asked concerned.
"It's Hermione, you know the Gryffindor Bookworm," Neville said hopefully.
"I know more of her than know her, why, what's up?" Hadrian asked confused.
"She's missing, because Ron insulted her after she tried to help him in charms, and from what Lavender told me is she is crying in the girls bathroom, so she doesn't know about the troll," Neville said quickly.
"Okay, and I presume you want to go and make sure she is safe?" Hadrian asked slowly.
"Yeah, could you come with me?" Neville asked hopefully.
"Penny is going to kill me, but since you have told me that she is one of the few Gryffindors who is nice to you, sure I'll go with you," Hadrian said before noticing that while talking their housemates had gotten a way up the staircase, and so followed Neville to where Hermione supposedly was.
"Hermione," Neville said as they approached the bathroom.
"Go away!" A girl's voice yelled from inside the bathroom.
"Hermione, there's a troll in the dungeon, and we are all supposed to be in our common rooms," Neville said urgently.
"Actually I think it is here, Neville," Hadrian said a slow thumping and a horrible smell was heard and smelt.
"Crud, we're dead, no way could three first years beat a full grown mountain troll," Neville said scared to death as he saw the troll enter their view, who seeing them raised his club.
"Nadal, bosnauk, dag kul izishu, nar kjani," Hadrian said in a language that caused the troll to stop suddenly and look at him in confusion and lowered it's club.(1)
"Hadrian, what did you just say?" Neville asked as Hermione came out and nearly passed out at seeing the troll who seemingly decided it didn't care what Hadrian said, and raised it's club again.
"Nar bosnauk hontum, throquurz, sma shara kul mir kjani, izg ha" The troll said as it swung its club at the three.(2)
"Um, run!" Hadrian said not understanding what the troll said but could tell it would not listen.
"But there is no way we can out run a troll," Neville said as he started to run anyway.
"But it's our best bet, I'll try and distract it," Hadrian said firmly as he pulled his wand.
"You'll die," Neville said shocked.
"I'll be fine, just run!" Hadrian said before starting to hum a melody which caused the troll to stop suddenly and grab its head, and dropped it's club.
"What just happened?" Neville asked confused.
"Quick, which of you can cast the levitation charm, use it on the club and then release the club over the troll's head," Hadrian said recognizing his humming was hurting the troll somehow, and how when he stopped it started to stand again.
"Wingardium Leviosa!" Hermione said as she did as Hadrian directed and managed to knock out the troll just before they heard footsteps running up stairs.
"What happened here?" Professor McGonagall asked as she saw the troll laying on the ground.
"Um, we beat a troll," Hadrian said simply.
"Why are none of you in your common rooms?" Severus asked coldly.
"Well, Ron insulted Hermione earlier and so she was crying in the bathroom and so we came to warn her of the troll when it showed up, then Hadrian started to hum and it somehow caused the troll pain, and so Hermione used our new charm and knocked out the troll," Neville said quickly.
"What do you mean humming caused the troll pain?" A white haired man with a wooden leg asked fascinated at the idea.
"I don't know, Professor Kettleburn, just when Hadrian was humming it stopped and was covering it's ears like it was in pain," Neville said simply.
"How strange, what were you humming, Mr. Potter?" Professor Kettleburn asked curiously.
"I don't know, it was just noises that felt right," Hadrian said simply.
"How strange, well I hope you take my class in your third year, and perhaps we can investigate it further," Professor Kettleburn said simply.
"Oh, yeah, sure," Hadrian said confused.
"Well I suppose due to going against what the Headmaster specifically said, you will each lose 10 points and have detention with your head of house, is that fair?" Professor McGonagall said simply.
"Yes Professor," They said in unison.
"Good, now Severus, can you escort Mr. Potter to his tower, and I will escort my Lions to their tower, and Silvanus, please take care of the troll," Professor McGonagall said simply.
"Of course, Deputy Headmistress, Potter, with me," Severus said before leading Hadrian to his common room.
AN: Hope you enjoyed, yes Hadrian does know the Black speech of Mordor due to his interactions with Balrogs in the last chapter of Harry's first adventure in the world of Tolkien. So yes that does mean that trolls in Harry Potter speak Black Speech and those parts are below.
1) Stop, friend, child is us, not food
2) No friend see, hungry, little man is good food, I eat
In regards to what he was humming, he was humming the melody of the song of Iluvatar again from that previous section of the greater story arch.