The Abyssgate was a large portal to the realm of the Abyss, deep in the heart of the Cometfall Sea's Crater above where the city of Ikariyus used to be. It cursed the ocean above and periodically released demons and aberrant beings into the waters for over a thousand years. Until its final closure, it was the largest portal to the Abyss on the surface of Abmarah.

While many believe that it formed as a scar of the Cometfall itself, it was actually formed immediately after the apocalyptic impact when Xaniv the Whisperer's star ship crashed into the newly formed impact crater. He fueled his intense hate of Varkanus into a ritual that turned him into an illithilich, the hate coalescing around the newly formed leyline to create the Abyssgate. The gate itself was anchored to Xaniv's soul.

Five hundred years later, the cursed gate opened in 2E571, and the demon prince Demogorgon emerged from it. The first council of the The Pirate Court was formed at Shipwreck City, where the mind flayer Xaniv with the help from 6 other lords pushed back the demons and sealed the Abyssgate and the Demogorgon.

The gate began to reopen slowly five hundred years later, during the events of the Curse of the Blood Sea campaign. It officially re-opened in 3E452. The reconvened pirate court fought back against Demogorgon and the demons once more, now led by the crew of the Phoenix Nebula. Xaniv used this re-opening to chain Varkanus himself, using the Black Scroll of Varkun to try and take over as the new god of magic. This temporarily turned the seas blood-red and the skies green worldwide. He was defeated in time by the crew of the Nebula, saving Varkanus and closing the Abyssgate for good. This destroyed the Abyssgate and lifted the curse from the Cometfall Sea.