Zargon

Zargon was an elder evil of unknowable origin, an eldritch abomination entombed under the ruins of a fallen city for his vile ways. The Devourer in the Depths demanded his endless voracity be sated, and if freed, would try to conquer the world and drown it in torrents of slime. Known as the Invincible Tyrant for his indestructability, even the ancient immortals could only trap him, for even if killed, Zargon always returned.

"Who can stand against the might of Zargon the Returner? Surely, no man is strong enough of courage and skill to face my master in combat. No god would dare confront him, for he has brought low others before. Nay, when Zargon awakens, all shall tremble as the world is born anew in his foul image."

- Dorn, Ascendant of Zargon

Description
Zargon was a truly repellent monstrosity, a horrifying, vaguely humanoid figure whose only resemblance to ordinary beings was a head, torso, and shoulders. His exact height was unclear, but his hulking mass loomed over most others; from the ground to his horn tip, he was about  tall, but he had been reported to stand as low as  and tower to nearly. The calloused flesh of his muscular torso bore marks from endless injuries, crisscrossed with oozing wounds, cankerous tumors, and smoking clots formed from the dribbling brown slime that fell from his chin.

Instead of arms, Zargon had knots of flesh at each of his shoulders, three on each side, from which six long tentacles, each tipped with a razor-sharp barb, lashed out like a whip. Similarly, he had six muscular tentacles at the base of his body, a wriggling nest of thick appendages that managed to propel his putrid form. The tentacles shot out, grabbing or stabbing the terrain to pull him forward, but also slithered and slid in the thick pool of gray goo that he was constantly surrounded in. Wherever Zargon went, a foul trail of blood, slime, and undigested body parts was left in his wake.

Though all of Zargon's form was abhorrent, when looking upon him, one's eyes were inexorably drawn to his hideous head. His reptilian visage hosted a wide maw filled with sharp, curving teeth above his dripping chin. A long, black horn with silver speckles (its reported length ranging between ), from the base of which oozed a pale yellow liquid, curved upwards and jutted out from the middle of his forehead. Outdoing all these traits in repulsiveness however was perhaps Zargon's most disturbing feature; his bulging, bloodshot, cycloptic eye.

Personality
Zargon was an entity unaccustomed to dealing with problems that couldn't be handled using brute force, physical or otherwise. He was so direct as to be reckless, his arrogance so great that he scoffed at gods, though his overpowering strength and tenacity compensated for such hubris. He blasted his enemies aside with powerful magic before crushing any that still remained, and even the imminent threat of death would not stem his ferocity, since he knew that even if destroyed, he would inevitably return. However, it was important to recognize that Zargon wasn't stupid. He was a cunning creature with great amounts of arcane and religious knowledge, a keen ability to recognize intent, and a powerful force of personality.

While certainly evil, showing callous cruelty to those that saved it, it was unclear where Zargon fell on the scales of law and chaos. On one hand, he was a rampaging creature of destruction driven by a terrible hunger and seemingly unending need to kill, a far cry from the traditional diabolical dealings associated with devils. However, Zargon's hunger for flesh and death could be tempered, and in a sense, he embodied a kind of primal tyranny. Upon realizing that his status as a "god" made getting victims easier, Zargon was willing to play the part, using his fearsomeness to demand worship. The appalling appeasements made to him came in the form of living sacrifices (preferably humanoids) for him to devour, as well as various treasures, and in return for regular tribute, he refrained from going on a killing spree.

Whatever horrible place Zargon originally came from, he showed little interest in returning. Part of the evil he embodied, as could be seen in the society that twisted into a vile reflection of him, was decadence. Even before being propriated, he found the ample supply of weak, soft prey (humans) to be to his liking, and their worship granted him many unforeseen advantages. Rather than try and take some distant plane, Zargon sought to rebuild the fallen empire around him, to mold a new kingdom in his own slimy image.

Powers
Zargon possessed ungodly levels of strength, and used his many tentacles to strike and constrict his foes dozens of times in the span of a few seconds. His appendages had great reach and the barbs at their end were perfect for embedding into flesh and bone to hold his victims still. If not simply crushing them, he could rip into his foes with his many teeth or gore them on his mighty horn. When fighting Zargon, the problem wasn't so much hitting him as it was trying to make any wound stick. He regenerated from injuries with a speed that surpassed that of a tarrasque, and his limbs would grow back (if he didn't reattach them first) in a mere minute if cut off. Acids and electricity were useless against him, and cold was of debated levels of uselessness, although he was not immune, only resistant to, fire.

The source of Zargon's immortality was his horn, without which he could no longer regenerate and would be substantially less resilient. Removing the horn from him would require formidable strength, and even if removed, Zargon still regenerated in a different way. Upon being slain, Zargon's corpse would be reduced to chunks of runny, slimy flesh while the horn remained intact, after which it would "regrow" him, causing his flesh to reform around the horn. In the past, this form of regeneration purportedly took years, but it had been known to happen in mere weeks if not days. More recently however, it was said that Zargon's horn would disintegrate a day after his death, and his spontaneous reformation would take place within the depths of Lake Moldvay beneath the ruins of the lost city of Cynicidea.

The only way to permanently defeat Zargon was to destroy his horn, and the only way to do that was to cast it into volcanic fire. It was disputed whether any lava pit would be sufficient or if it had to be the Eye of Zargon, a bubbling pool of magma also underneath Cynidicea said to glow as redly as Zargon's own eye. The smoking crater was surrounded by fire elementals, salamanders, lesser efreeti and other monsters, and one would have to cast the horn in before it disintegrated.

Magical
The gods were unable to discover how to destroy Zargon's horn. As an elder evil, Zargon was immune to all divination spells of divine origin, and he had a generally horrible influence on divine beings and their followers. All divine spellcasters within of Zargon, despite being able to cast the spells they had already prepared, were prevented from receiving new ones.

Various other magical effects applied to him at all times, including truesight, tongues, and nondetection. He had various spell-like abilities, including the power to create magic circles against good at will, shoot waves of slime and lightning bolts thrice a day, and create an acid cloud and mind fog once each day. He had a preference for lightning bolt, slime wave and mind fog, but was cautious enough to reserve acid cloud for when foes got close.

Slime
Despite being able to exist indefinitely on land, Zargon was an aquatic creature that swam faster than he crawled. Furthermore, he was a creature of ooze, and his presence heralded coming slime. A gray grease covered a radius around him wherever he went and persisted for a minute after he left. He also had the power to summon oozes known as corruptures, cancerous creatures that came into being wherever wilderness was warped by poison and sickness, or where the normal laws of reality were repeatedly broken.

Part of what made Zargon an apocalyptic threat was his foul slime. Every few dozen seconds, he could spew forth a massive deluge of acidic, brown goo from his horrid maw, and those he bit into were also infected with the substance. Over the course of several days, if not treated with a remove disease or heal spell, those polluted by the slime had their vitality, intelligence, and personality slowly reduced until they either collapsed into puddles of grime or transformed into the terrifying humanoid oozes known as the whelps of Zargon. Whelps were mindless killing monsters with only the barest sense of instinct and horrific hints of their past, and continue exposure risked infection with the same vile pollution that had corrupted them.

Even worse was Zargon's effect on the world around him. Zargon's corrupting influence, (the combined, unintended effect of countless innocent deaths, the worship of his cultists, and the manifested unrest of the gods) contaminated the land and caused the emergence of eerie weather patterns. Most notable of these meteorological distortions was when it rained the same brown slime as was found within him, a slime that contaminated all exposed water and any who came into contact with it. The activities of Zargon's cultists to awaken him could worsen this weather manipulation, expanding its duration and area of effect. Were Zargon to fully escape his prison, the entire world would be subject to hourly, overlapping, atmospheric disasters, and no one would be safe as his foul slime rained over all.

Activities
Zargon was known to take on selected warlocks as their patron.

Rumors & Legends
One legend states that Zargon was the first ruler of the Nine Hells. When Asmodeus first rose from his fall, he defeated Zargon and its armies with the help of his devilish children. Zargon was defeated, but its horn could not be destroyed. In frustration, Asmodeus cast it into the Prime Material plane, where it struck in what later became the Raurin desert and was buried deeply. Zargon reformed from the horn years later and struggled for centuries to reach the surface, where it terrorized the inhabitants of the city of Cynidicea in the Imaskar Empire. They eventually came to worship Zargon like a tyrannical god-king and sacrificed many to appease its hunger. It was said that some deities then tried to destroy Zargon, but it killed a few of their avatars and the rest retreated in defeat. Asmodeus (being unaffected by Zargon's anti-divinity aura) decided that Zargon was too dangerous to be allowed to remain free, so he encased Zargon in solid rock and then buried the Cynidiceans alive so they could not release it again.

It was rumored that Zargon slept fitfully, deep beneath the Giant's Belt Mountains on the edge of the Raurin desert. In those mountains, a brown dragon was said to watch over a sandy basin known as the Valley of Death to ensure that nothing aroused Zargon from slumber. Who or what bound the dragon to this task was unknown.

Other stories proposed that Zargon was a Demon Prince that was thrown out of the Abyss.