Seven Seals - Holy Book of Seals

After finishing quest 5 you should be standing at Wood (Priest) in Einhasad Temple Town of Aden . He will ask you to contact High Priest Orven for a decryption.
Talk to High Priest Orven (standing nearby).
Orven himself is not able to translate, but he knows who can do it. Take the letter from him and go to Leopard in Town of Goddard.
Decryption Expert Leopad will study the Sealed Scripture, but will not be able to find the decryption key.
However, he will remember his teacher, who can help with decoding. Exit Goddard.
You'll find Grandmaster Rolens on the eastern exit of the city.
Start a conversation with him. Talk about Sealed Scripture. He will be very surprised.
At this moment, the mob Shilen's Evil Thought (lvl.), familiar to you from the Seven Signs - Dying Message quest, will appear. After killing him you will receive a Suspicious Statue.
Continue the conversation with Rolens.
He solved the code and said that a book with a similar code was in the Rune Library. Go to Rune Township in Mystic Guild. Look for Library Director Sofia who runs the Arcane Library.
She will give you the Manuscript of Mysteries.
After receiving this manuscript, return to Priest Wood in Aden.
This ends the quest and you will receive 52,518,015 experience and 5,817,677 skill points.