Just as life springs forth from decay, so too may the unnatural come to serve the natural. The heart can be made into a stave of shifting form, but I will need a vessel strong enough to contain its power. There is a barrow den near Starfall Village, in Winterspring. The true entrance will only reveal itself if you are alone. Within is a keeper who lost his way long ago; Nandieb. His stave shall be the heart's vessel. It pains me to suggest, but he is no longer the great keeper I once knew.