The Gatekeeper's Crystal is a powerful magic device, according to legend, created by a powerful lich. It is made up of three separate shards, each of which are powerful in their own right, but devastating when brought together as a whole. When the crystal is used as a whole, its three shards separate and scatter across a vast area, including other planes. When assembled, the device looks like a three-pointed star almost 1' (30cm) in diameter.
The crystal was used around a thousand years ago (the current year being 1374 DR) to destroy the defenses of Myth Ondath. It was used in 1369 DR by the Harpers to raze Hellgate Keep. One shard was found in the ruins of Hellgate Keep by Sarya Dlardrageth. Sarya found another in 1370 DR in a volcano in Avernus. In 1371 DR the mages of Reilloch Domayr located one of the shards and kept it in Nandiyerron's Armory in Tower Reilloch until it was stolen by demonic invaders in 1374 DR and returned to Sarya, thus completing the device.