Appearing to be but a simple decorated greatsword. The steel needing a bit of a polish. But the edge keen and a large emerald set into the cross guard. The blade is actually a wizard caught in a powerful curse, unable to free himself, but capable of thoughtspeech after attuning to a wielder. He may even cast some spells while in combat to help out.
Whilst exploring underground the PCs discover tube like tunnels stretching for miles, upon further inspection the strange tunnels seem to connect all major cities in the are, what is their purpose?