I see what you're asking. You need to get Ancient seeds from killing various types of Greydwarves. Black Forest crypts have a chance to contain a tablet that tells you the location of the elder, who you defeat for the key drop. You need to keep the "Swamp Key" with you at all times when you go to these crypts. When inside, use your pickaxe on the mud to venture further and get some sweet loot! The bones should be in there.