A fragment of the shattered medallion is all that I can offer. You must find another of dragon blood willing to assist you in forging a new key. Once you secure this key, you must travel to the Wyrmbog in Dustwallow Marsh. It is there that you will find her lair, adventurer. Where to find other flights willing to help? Sadly, I do not know... They are said to exist. Some may even work and live among us, disguised as one of the humanoid races. I wish you luck.