The Murkenstone
The Murkenstone is a vile artifact that is the heart of the power of the Dark Lands. The stone is a piece of The Interloper moon, the planet upon which the three of the Unholy Trio were born. It creates Murkenshades and is core to the fuel and functioning of Curtain of Night. Its foul aura and power is fed continuously by the Quest of Black Tears.
Its EXACT location is not known, it confounds scrying and such things, but it is thought to be deep in the Dark Lands in a holy site.