Clue

As soon as Noel stepped inside the hidden room, there was only one book in that place since this was the place where Ardagan slumbered previously.

It was the notebook of his ancestor that he didn't finish in his dream because of what happened during that time.

He carefully opened the book and saw the first few sentences in that book. The words were exactly the same, so it meant either Ardagan or his father had read this book.

Noel looked around to find any more clues, but since there was nothing but stone wall inside, he decided to walk back to the office and put the book on the table.

The book wasn't that thick, so he should be able to finish this book in one sitting.

But to his surprise, when he lifted the book up, a letter fell down to the ground. 

"This is…" Noel widened his eyes in shock. He carefully picked up the letter and opened it because he never saw this letter in his dream. Even the paper looked new.