Find Prospector Khrona's Notes and Prospector Soren's Maps at Brann's Base-Camp.
With Norgannon's Shell in hand, only half of the archive key remains to be found. Luckily, I've had the Explorers' League hard at work chasing down leads about the whereabouts of Norgannon's Core.
Far to the southeast of the Inventor's Library, on the slopes to the north of Dun Niffelem, is a camp bearing my name. The Explorers' League representatives seeking the second half of the key are based there. Bring me the maps and the notes they've made and we should be able to track down the other key half.