At the heart of Regadnîn is Piranoth Cyst. This enormous sink-hole is five miles across, plunging a mile down. It was an egress point for the primordials and their armies in the Dawn War. It started when the primordials opened a rift between Chaos and this area of a world then called Sphere 411. They came up the slopes of the great pit, assaulting the armies of the Nawirrûs Covenant.
The many invasions and tens of thousands of enemy that came through this rift was led to it being called the Piranoth Cyst; named after the Primordial Lord Piranoth, creator of the worlds that make-up the Abyss.
In 209, on Nindonor's first expedition into Regadnîn, he found a vast sink-hole. 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 the coffer was an ancient scroll written in Supernal - the language of the gods, that reads:
... 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 should be able to destroy the 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 against it. It fell under Sig Mak Gan, purging the world that Bal-Kriav so nobly died for.
... 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 Dawn 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.