Throgin makes it safe around back to the party and explain he saw a large fountain in a room to the North but didn't risk to look into the room and check if there are other corridors leading from that room. You can always return to that room later - you decide and move on.
You move back and around the balcony and enter the next wide but short tunnel: A giant stone skull crusted with moss juts out from the end of the passageway. A flame flickers within each of its eye sockets, and a view into a chamber beyond can be seen through its open jaws.
A stone sarcophagus stands at the center of the chamber you can see through the open jaws, its lid adorned with a coiled serpent carved in relief. Behind the sarcophagus, resting atop a marble pedestal, is an ornate crystal box with a small humanoid skull floating inside it.
OOC:
The skull's jaws are opened wide enough to allow a Medium or smaller creature to climb though.
A detect magic spell reveals an aura of transmutation magic around the skull. Vatoris informs you