The Dark Planet

Archaeologists tell of a strange, black substance uncovered at intersections between major Ley Lines and Song Lines throughout the lands of Yore. This unnatural-seeming substance resembles obsidian in its texture and appearace, yet like a metal it cannot be shattered, and like a rock it cannot be bent.
It has been discovered in great jagged lumps at the bottom of mephitic craters, sinkholes (including the great Morgrod basin of Qualimor) and swamps, where it pulses and throbs with a seemingly occult and unholy power. The Shadowmancers of Qualimor guard it well beneath their dark tower, and in other places weird cults gather to worship its ineffable alien presence.
There are some astrologers, shamans and Fateweavers who believe this substance to be fragmented parts of a meteor that crashed into Amarthaur millennia ago, and which was originally a part of the fabled Dark Planet. The night sky holds many bright stars and gleaming planets, but one remains hidden, only betraying itself by an absence of light. Its impenetrable surface is only occasionally illumined by the Blood Comet that completes its orbit every six centuries, as catalogued by the Xin people in the 15th century. Strangely, they referred to the Dark Planet by a name that was unpronounceable in their own tongue: Yuggoth.
Excerpt from the Histories of Jharpur of Golden Huzuz, the City of Delights. Donated to the Great Library of Zobeck, 1848 N.E.

The Coming of Yuggoth

Look to ye sky, and tremble ‘neath its vault
When thou seest the comet that burns as blood,
For in its wake, without relent
Doth approach from vast gulfs betwixt ye stars
A dark planet, Yuggoth called.

In its deathly shadow ye forests shall madden;
Abyssal lords shall vie for mortal souls,
And in desperation Heaven and Hell shall unite;
Orc and Elfin, Dark-dweller and Light,
In vain denial they stand shoulder-fast.

Ye terrible Mistress of Wyrms doth rise in fury to contest,
As ye daemon herald, Cassius,
Who eluded somehow Nyte’s sorcerous bind,
Doth reveal himself from his hidden hole,
And pronounce the Second Darkness come at last.

Ye Black Pharoah shall be enthroned,
And rule all Yore with merciless dread;
Cities shall fall, and armies shall burn,
As Ghoul and Shadow make unholy pact,
And from aeons of slumber, the Great Old Ones shall stir again.

Transcribed from an anonymous Abyssal text, plundered from the Ruin of Tsen c. 771 N.E.