While I believe that the weapon was destroyed, think about the ramifications if it wasn't. It is an artifact capable of annihilating whole armies of powerful Elemental creatures, and seemingly turned the fate of a cataclysmic war single handedly. Now, the cost of doing so was the mana life-force of a city, but think about this:
A) The Fissure
B) The Capitol's Shard of the Mana Core
D) Theano and the Manaphages
We know the first three are potentially the greatest sources of mana on Lore, so if there is anything that can currently power the artifact it is probably those three.
Another point - The Fissure has been leaked for a long time as being a critical point in the plot. If someone is trying to use it as a power source to wipe out their enemies, that could make sense.
Another point - The Capitol has a superweapon that they believe can annihilate all opposition. We don't know what the Proclamations are, and not everything lines up, but keep it in mind.
Another point - Theano has openly stated he will bring back a weapon, and with the Manaphages he is capable of collecting vast amounts of mana. Belle also features in this saga, so...
Not everything works, but I think there are aspects worth considering.