Like almost everyone you talk to and almost everything you read in there you need to destroy the bone totem and then talk to a miner...
The game tells you exactly this.
I'm stuck at this as well and don't know what totem this is. I don't recall any NPC, book, or quest talking about something like that.
I've got Leandra's Blood and the only place I can think of going to find out how to make the Death Knight spell is the mines.
Seems like I keep overlooking something or other, yet I read everything I come across...
I'm still supposed to find the Skeleton King's Summoner, yet I know who it is and even told Arhu. I was supposed to find signs of Source in Sacred Stone, but never did, yet the quest's finished now.
Anyway, the only thing I have to go on that's relevant to what I'm trying to do is a quest entry saying "We reported to Icara with the vial of blood... She'll tell us where to look next." Except that she hasn't told me to look anywhere but the mines.