I obtained a strange orb, with a small glowing light in the middle while venturing within Vulak'Aerr's Dominion. When I claimed if from the riftkeeper's corpse, I felt a surge of magical energy. It seems like this is a magical focus, and might be what the riftkeepers are using to open and sustain the portals to Ethernere. If I can gather more of these foci, I might be able to use them to close the portals and slow the advance of the Awakened into Vesspyr Isles.