On 11 War March 1501 DE, an enormous sink-hole, five miles across, one deep, opened in Regadnîn. It became the mouth of a rift linking the world Bal-Kriav with the Sea of Entropy. In the Creation War (1486 DE - 8777 DE), it was another primordial invasion point. By way this inter-system rift, primordials spilled out of Chaos, slithering, crawling and climbing up slopes towards the citadels of the Nawirrûs Covenant.
For hundreds of years, Piranoth Cyst was a recurring problem for the Covenant, one of many unstable areas across Regadnîn's war-torn wastes. Some of the dangerous of that time still roam this sinkhole.
In 209, the Grand Purveyor Nindonor made his first expedition into Regadnîn. At Piranoth Cyst, his dig team found a shattered gateway at the bottom, broken and mostly buried. Before being driven from the area by deadly magical storm of falling iron, a living spell, Nindonor was able to make out elaborate runes on a broken arch. One of these runes was the key to unlocking a coffer he had pilfered from Aphalur. Inside, ancient scroll written in Supernal:
... our victorious angels looked for a means to shatter the arch and seal this gateway to Chaos. Great magic, divine spells, and physical attacks failed to affect it. So, I forged three relics. When combined, they may have a chance in destroying this primordial device. The Sig Mak Gan is our only hope in destroying this Entropy Arch.
... with shield, gauntlet and pick-axe, I laid a dozen blows. Cracked, shattered, it fell to Sig Mak Gan.
... to safeguard these great items, each will be put in the security of an Archangel.
- Naraz-Nâru, from an ancient scroll - "Arch of Chaos"
A Scroll of Dawn says that on one of Nindonor's forays to this area he met a primal air elemental named Tuffulus. This elemental told him that in the Creation War, the sink-hole opened into Chaos. It was the invasion egress point for the primordials and their armies. He went on for hours talking about the battles with the gods, as if he had been there. He then told me that one of the most dangerous primordials to come through this gateway was Nakh-Zennîm.
I served him, and continue to carry out his last command ... "It all must be destroyed and returned to Chaos". Luckily that I was a priest of Arcana and had a Word of Recall. Let this be known to all that read this scroll, many of the terrors of Regadnîn still carry out their last commands.