Ah, Felo'melorn. I am familiar with this weapon.
For ages the Council of Tirisfal attempted to recover the blade. Its control over the primal forces of fire would be devastating in the wrong hands.
As luck would have it, an associate of mine, Archmage Modera has recently uncovered some information on this artifact. This crystal contains a message from her.
I suggest you start your search there. The portal over there will bring you back to the city.