When you start the quest and Ziva talks to you about the gem, go downstairs twice, and go left and enter the room to the left of the statue. Read the journal on the desk, about the enhanced fertility potion, and it will say something about taking the gem west. Go to Weirdwood, and then west until you see the burnt patch next to the inn. Check out the burnt patch, and you should find a chest with the recipe for enhanced fertility potion. Go to thebinn and talk to the innkeeper about the burnt patch, he will start talking about a beast, keep talking until he tells you how to get there. Then, you can go south to the dragon's lair. The dragon will show you where the gem is. One of the skeletons will also have a key that opens the door. You will have to choose to use the key to open the door and steal the gem, which the dragon will chase and try to kill you, or you can return to the dragon, and she will offer you gold instead. Insist on taking the gem, and she will make a deal to fertilize her eggs in exchange for the gem. She will change to a more human form, and have a sex scene. Afterwards, return to the inn, stay a few days, and return to the dragon. If she's pregnant, she will give you the gem.