Bring the mold to Alard Schmied in Dalaran and have him help you forge a new set of keys. Return to Tae'thelan when you have the finished set.
I'd like you to take the mold to the blacksmith in Dalaran. Alard, I believe his name is.
Have him help you forge a new set of keys.
I found some writing on the back of the mold that may hold the answer to what these keys unlock. I'll stay here and try to translate the text.