From The Heretic Knowledge Vault
The otherwise unnamed site of the big battle between the elves who are trying to awaken Senilis, and Sarine's party, which is trying to stop them, or at least talk them out of it. It's first mentioned here by Sarine as she tries to enlist Tsuiraku in her quest to slow down the elves, without success. Tsuirakuan General Izayoi shortly lets on that he knows about this place, too, as somewhere "beyond the dwarven ruins."
When Sarine, Meji and the Amraphels arrive in this mysterious place, it's revealed as a set of ruins in their own right, although whether dwarven or of other origins isn't totally clear. Sarine says that earthquakes along a "major fault zone" leveled the city that they gate into, although the details are unclear; in particular, she doesn't know whether it happened "before, during or after" the disappearance of the dwarves. Presumably all will be revealed in good time.