Chemnosit

Great Doom Chemnosit, the Monarch Worm

Like its cousin Xotani, the worm called Chemnosit is described in various garbled texts as a burrowing creature, with a whipping and flailing form some 500 feet long. The similarities of their alien and aberrant biologies, however, end there. Taken from a svirfneblin record-tome called the Way of the End-Name, itself recovered by Pathfinders from a treasure trove formerly belonging to a debased hive of skum deep within Sekamina, this passage purports to describe the Monarch Worm in great detail:
This is the demon worm that eats the heart of the world. It rears up like a snake about to strike, possessed of a huge, multipartite mouth filled with innumerable teeth. Within the pit of its mouth is a huge and evil eye, around which whip dozens of long, thin tendrils and other tentacular appendages ending in chomping mouths. The vast thing’s body is heavily armored with elaborate spikes and protrusions strangely reminiscent of the exteriors of cathedrals.
How much of the description is accurate is unknown; it is said that those few who lay eyes upon the beast Chemnosit are forever warped and made unclean.

Lore

Alone among the Spawn, the mighty Monarch Worm is still thought to be active beneath the surface of Golarion, slowly creeping between the cracks in the world, causing unpredictable earthquakes and wild tremors, bent to the completion of unfathomable duties and unspeakable needs. It is worshiped, in a weird and terror-shrouded way, by the translucent-skinned humanoids who dwell in the most haunted Vaults of Orv, and foul blood-drinking rites invoked around sputtering flames are spoken in Chemnosit’s unhallowed name throughout the Darklands by inhuman, flopping figures.
According to the gibbering prophecies of these abhorrent tribes, and confirmed by what little can be gathered from the wrecked libraries of abandoned drow and duergar cities wiped away in the wake of Chemnosit’s infrequent assaults, the Monarch Worm kills primarily by use of its awful, unblinking eye. The confused tales of those unhinged and hobbled few who have borne witness to Chemnosit’s gaze and survived describe enduring the depths of final famine, feeling their very minds falling away as a hunger unlike any other overtakes them completely, until their desperate need to consume surpasses the very need for survival. Some scholars of the Clockwork Cathedral in Absalom categorize the disturbing results as “autocannibalism”—the victims tear into their own extremities, devouring still-warm hunks of their own bodies until, stuffed full of their own flesh, they vomit. And then they eat more, all under the quiet, watchful eye of Chemnosit. Those who perish, those who flee in terror, and those who fight—all become the food of the Monarch Worm.

Summoning

Folklore claims that dread Chemnosit can be called forth with certain powerful magics involving ritual sacrifice, although there exist no known means to control the bestial titan once it appears, or even to attempt influencing its rampaging, ceaseless hunger. Some dwellers in the benighted depths of the Darklands, particularly within Sekamina, seek a way to leash and guide the godlike form of the Monarch Worm; it is theorized that the majority of this Spawn’s assaults on cities are the result of such tampering.

Species

Spawn of Rovagug