Mythallar

This magical device looked much like a crystal ball but was about 150 feet in diameter. The globe shed a very bright light—similar to the disc of the sun—with dimmer shadows and shapes moving across its surface. An ornate stand kept the perfectly spherical device in place.
Touching a mythallar was a lethal decision. Anyone who touched the device was instantly slain. Any item that touched it, except the stand that contained it, was instantly disintegrated. Any undead that touched the mythallar were destroyed.