Somebody challange it?

It can be found in Heidel Castle, if you run all the way to the throne room. Once there, turn left through a small doorway. Personally didn't need the quest for it. I didn't need the quest to get it, found it by simply exploring the castle.

Heidel Castle is literaly out of Heidel City, go to the north road after Vanacil and keep right and you'll find another entrance, cross the entire town, guards have purple name even for a 62 level characther, but they die prety easily for 250+ AP (I don't know the minimum AP requirement), once you cross the town you find a room with two lions holding a shield and a empty trone, go left and read the book to get knowledge.

ty for info