Personally im going with blackreach. We might find out more about the Falmer and the Dwemer while dwelling there.
I'm feeling Reach vibes. But most likely vampires and the Reach both.
I thought it referred to the heart of Llorkhan. Kagrenacs used his aetherium tools on heart of Llorkhan which made the entire dwemer race dissapear. I hope dwarven armies come back from the void with vengeance!