Tholaghru or Tholaghru the Gnasher is the common name given to one of the Elder Powers. He (or possibly It) holds the portfolios of mutation, chaos and disorder; in other words, the creatures in the world as they physically degenerate, but also an insatiable desire for “the new.” He also holds the portfolio of animal instincts – that is to say, swift and violent reaction to being threatened in any way. He is aligned with Evil.
Popular conception portrays Tholaghru as a gnarled and festering god-being, writhing in eternal pain. Legend holds that the entire plane of Stygia is built atop his gnarled and festering back, though how literally true this claim is is debatable (and possibly itself mutable).
Worshippers of Tholaghru have little organization and few if any religious texts in common, but the symbol most commonly used to represent Tholaghru is a simple, scrawled semi-spiral that represents increased disorder and disassociation from a central stability.
The cult language of Tholaghru is a rapidly spoken, guttural tongue that has no word for itself but is known by outsiders as Yovendish. It is filled with odd inflections and is difficult to master, as syllabic emphasis on any particular word changes within context.
Tholaghru is the Power of both slow dissolution to ruin and also the Power of sudden, catastrophic failure.
He is not necessarily malicious even though his actions often cause suffering; rather, he may be seen simply as a callous, dispassionate entity that actively promotes extreme Darwinism - “evolution in action.” Tholaghru is not always content to allow evolution to proceed at its own pace; as he craves ever-new experiences, he is sometimes wont to “help evolution along” a bit by deliberately causing catastrophes and pushing forward mutations so as to cull the weak and allow the strong to push forward as he searches endlessly for new stimulation.
Tholaghru’s physical essence is in eternal pain, but this is only part of his portfolio; he is receiving eternal stimulation of every variety, from eternal pain to eternal ecstasy. Every new demon that Descends brings him something new and he is somehow able to share the sensations and memories of all demons that come in contact with him. It is for this (hedonistic?) reason that Tholaghru constantly encourages the ranks of mortals to curse the Powers and turn toward evil... he wants them to bring to him ever more stimulation of every sort, and those who do not turn to evil will never be able to bring him the taste of more profane stimulations.
Tholaghru was the primary shaper of the world in which Petra lived. While humanity was able to develop advanced technology, it was no thanks to Tholaghru's influence, for the world was sickly, misshapen and (ultimately) dying, inhabited by sickly and misshapen humans.
The home realm of Tholaghru is known as the Great Maze. It is a realm of madness, chaos and confusion governed by nothing resembling natural order, though visitors to it may inadvertantly impose some logic of their own upon it by virtue of observing it. It is rarely accessible from the planes of the Nexus, though a part of it could briefly be visited during Petra's Breath.
Wyrm Masters and the creatures that they command are largely formed from the chaos and mutations that shear off from the corrupted flesh and mind of Tholaghru. The connection between Tholaghru and the Doom Howler is subtler, drawing on his power to nurture a sort of undeath where physics and reason would bring certain death.