If you remember back to our Quel'Delar post (I know it was a different world back then) here's the sword itself, according to World of Raids. The sword definitely appears to bear a certain kinship to Quel'Serrar in terms of its appearance. We've also had reports in the comments that the Quel'Delar quest chain involves the Sunwell in some way - picking up where patch 2.4 left off, perhaps? The more we learn about this sword, the more interesting it becomes. Is it a trick of the Lich King? The famous Runeblade left behind by the Sunstrider dynasty? As of yet, all we have are tantalizing glimpses. I personally hope to get to see more soon.