Orb of Ghrond

An Orb of Ghrond is an obsidian ball that offers a terrible glimpse into the Realm of Chaos, revealing fragments of the future in the swirling vortex of maddening energies. Anyone other than a Dark Elf who looks into the orb risks going insane. However, in exchange for the almost assured madness, a viewer gains a clear look at some important future event.

Ghrond lies in the frozen north of the Witch King’s domain. A black tower, it rises like a spear from its mountain spur. Here, foul sorcerers stare into the abyss that is the Realm of Chaos to catch glimpses of the future within the changes of the multicoloured storms raging there. Occasionally, a tendril of raw energy snakes out and licks the stones of the mountain, creating black orbs that serve as windows into this terrible place. The sorcerers smooth these stones and use them to divine the future to report back to the Witch King to help him plot his foul strategies for launching attacks against the world. And very rarely, some daring or foolish individual steals an orb for the promises of power they are sure to hold.

Source

 * Warhammer Fantasy RPG 2nd ED -- Realms of Sorcery (pg. 206).