A Mage's Knowledge

You've got some good spells for a novice mage. There are a few things holding you back, though. For instance, it's absolutely clear to me you don't know Polymorph. If you did, you would've been using it on the harpies that were attacking us! Let's fix that. My spellbook has details on how to cast it... but my captors threw it into the nearby lake. Grab it for me, would you? Oh, and don't look through the book beforehand. You will almost certainly regret it if you do.