Luckily you can find one very earily in Act 2... I was frustrated by this as well.. I couldn't go back to the merchants to ID all the goodies I found because I went to Act 2. <img src="/ubbthreads/images/graemlins/disagree.gif" alt="" />
On a related note... when you click on the key on the ground it says the battlefield is unlocked... Do you actually have to physically pick up the key and have it in your inventory? Not that it matters, just want to make sure. Seems like you don't... because you have to do the drag and drop action to pick it up, it's not like a normal item.
