Disclaimer: 
Harry Potter and all of its characters belong to J.K Rowling.
I own nothing but the original characters I make.
 
"Dialogue"
'Thoughts'
$Parseltongue$
 
Chapter 20: The Underground Chamber

Harry groaned as he walked through the empty halls. Snape did not stop asking questions until he got one wrong and then proceeded to mock him for his ignorance in front of the class, something that the Slytherin students had found very amusing.

The question was about the brewing process of some potion he had never heard of, but he was sure, was not part of Hogwarts curriculum, since even Hermione had her hand down with that one.

"Tsk, what a petty man!." He was at least thankful for the complete absence of people in this part of the castle as he did not want others to see him like this.

'Control yourself.' He admonished himself for his outburst.

Harry closed his eyes and focused his mind. All the negative feelings were washed away, like the current of a river, and his calm demeanor returned once more. This was one of the many uses of occlumency.

He had to give Snape some credit. It was not that easy to rile him up like this, but the potion professor seemed to have a special talent for it.

His piercing green eyes moved around and stopped at an object hanging from the dull stone wall. It was a painting of a woman drinking tea in a peaceful meadow.

People would pass by that painting and not think anything about it, but this was not going to fool him. This painting was one of the many that were placed around Hogwards with the purpose of spying for the Headmaster.

This part of the castle was always empty, except for the first day of classes. The corridor ahead of him was the one that led to the underground water cave where the first-year students arrived with their boats.

But there was one more, very important, thing in this area, it was something that only two people in the castle knew about it. Well, it was three people now.

"Obscuria" a dark cloud of smoke came out of Harry's wand and covered the painting as he walked past it and as soon as he was out of its sight, the cloud dissipated, leaving no trace.

The entity inside the painting would be unable to detect any trace of the dark cloud of anyone who passed by it for the duration of the magic, as this was the purpose of this particular spell.

Harry saw an opening to his left. At the end of a short corridor, was a closed door that led to the water cave. This door was only opened by a professor when the first years entered the castle and remained closed for the rest of the year. 
Ahead of him was a dead end. A short path that ended with a wall and a big painting hanging from said wall.

It was a painting of a wooden wall with a stone frame, similar to many of the real doors of the castle.

A boring painting for a boring area of the castle. At least that's what most people would think.

But Harry knew better. He knew things that only the Master of the castle could know, for he has been, albeit for a short period of time, the Master of this castle, or at least, an alternate version of it.

'Let's hope this works then…' He could not assume that all thighs were the same as he knew. But this was something he had to at least try, for it could bring him great benefits and make the coming war more manageable.

Harry walked until he was right in front of the painting and observed it very carefully. 
He scanned every inch of it for a few minutes until he was satisfied with his findings.

"Yes, this should work." He smiled.

He took his wand out and started to tap on the painted stones around the wooden door. He taped ten of the stones in a very specific manner and order before stopping, and then he waited.

An empty moment later, on the stones that were tapped, appeared some runes that started to shine brightly with a blue light, and then, a click could be heard.

Harry placed a hand on the left side of the painting and pulled hard. This one opened in the same way a door would, revealing a descending set of stairs that disappeared into the darkness.

"Lumos" A strong light appeared on the tip of his wand and he started to descend the stairs with no hesitation, like he was already very familiar with this procedure.

The stairs continued for quite a while, descending further and further down. Followed by them, was a narrow corridor that ended into a stone arch.

Harry walked past the arch, entering a massive chamber completely covered in darkness.
"Ah…the foundation of Hogwarts. It never ceased to impress me."

As his voice echoed through the chamber, a blue magical fire came to life, illuminating the colossal room with an eerie light.

The place is already impressive by its size alone. He knew for a fact that this room was almost the size of the entire castle. 

The floor was made of some fine, polished stone and there were massive columns all over the place. Those columns were dozens of meters in diameter and were made of some pure white stone he was never able to identify. Across its surfaces were countless archaic runes from an era long lost and their height was hard to calculate as they got lost in the darkness, way past the area that was illuminated by the fires.
In between some of the columns were stone golems made of the same polished white, marble-like, material. And like the column, these golems were covered in the same type of runes.

The golems remained stationary in a kneeling position as Harry walked through the chamber. He gave the constructs a passing glance.
'if someone were to enter this place uninvited…'

He felt goosebumps just thinking about it. These constructs were not there for decoration, and if an intruder entered the chamber without following the proper procedure, that person would be in for a very painful death.

But that was not important right now. The golems were not the reason for this visit. His objective lies further ahead.

Harry continued traversing the colossal chamber under the blue light offered by the magical fires until he reached the center.

At the very core of the chamber, deep inside the bowels of the castle, was a circular platform, and in the middle of it was a crystal.
The crystal was easily ten times his own size and was shaped like an elongated diamond. It floated a few feet in the air and kept a constant rotation while emitting a pleasant sound.

This was the arkstone of Hogwarts. It's very source of power and the biggest magical stone in the whole world.

And of course, the reason he came to this place.