But it's fun to work it into the story.
Indeed, I have read haughty interpretations of the habit of having the wise old man tell all that manage to find all sorts of political implications without noticing the most obvious aesthetic one: that it's not very interesting to have your hero pouring through the books. And not even books that the reader would read for fun. (Robin McKinley's Beauty probably has the library I would most like to read in. Perhaps because other fantasy libraries, however lovingly drawn, aren't for pleasure reading.)
Not that finding out by practical research is all that much more interesting. Especially when failure means being smashed to smithereens.
Ah the fun of giving your monsters' history and so its weaknesses.