Obviously, one who works in a library, such as the Imperial Library.
The vast majority of librarians on Dragaera belong to the House of Lyorn, although in a large library, members of other Houses are not uncommon. Given the intellectual natures of the members of the Houses of Hawk and Athyra, these houses are likely well represented in this capacity.
The best ones are highly skilled in research, drawing together disparate clues in scattered documents in order to bring forth new information. Tsalmoth librarians are noted to be excellent in this regard due to their tenacious natures. Others with a persistent streak, even Easterners, can also do quite well.