Sixth Great Maelstrom, is a term used by wraiths to describe a violent superstorm that happened within the Shadowlands when the Week of Nightmares struck the entire world around 1999. Also known as the Dja-ahk among the immortals, this was the last Great Maelstrom of the Classic World of Darkness.
The storm brought by the Sixth Great Maelstrom is unique, caused entirely by events in the Underworld rather than triggered by tragedy in the Skinlands as previous Great Maelstroms were. Metaphysically, it is the most important event in the World of Darkness until the Time of Judgement, even eclipsing the Week of Nightmares.
The Maelstrom occurred in 1999 (Anno Stygiae 54 Post Quintum) during the assault on Stygia by the Yellow Springs, the underworld of Asia and the empire of Yu Huang. The soldiers of the Dark Kingdom of Jade, with the treasonous aid of the Smiling Lord, assaulted major Stygian strongholds throughout the West, with the Hierarchy barely holding on only due to the bravery of its defenders and the extremely shoddy equipment Yu Huang had manufactured in bulk for the assault.
At the time, the rest of the Stygian military was partly paralyzed; they had received word from the Ferryman Severus (via his apprentice Erik) that the underworld vampiric city of Enoch actually existed. The warning that caused this siege was actually a subtle manipulation of Stygian society by the Ferrymen, who in turn were fulfilling an ancient debt to Anubis, the grave god of Amenti, the Dark Kingdom of Sand. To the Undying, Enoch was an obscenity, and its destruction was a major victory in the eternal struggle between Horus, Osiris and Set. The Hierarchy sieged Enoch for several weeks until they finally used a relic nuclear weapon to destroy the city.
At the same time, in the Labyrinth, a Void Engineer, Xerxes Jones, prepared his greatest experiment: detonation of a second relic nuclear device in the mouth of Oblivion. Interesting idea, bad timing.
The result was the most potent physical and spiritual destruction in the history of the Underworld. The carnage led the labyrinth to vomit forth armies of Spectres under the control of the infamous Nephwrack, Coldheart. These armies in turn assaulted the Isle of Sorrows, Stygian outposts, soldiers of the Yellow Springs, anyone they could find. Stygian society buckled under the strain.
And then Charon, absent since 1945, returned; however, the loss of his memories, held by the persecuted Mnemoi Guild, was too great. He Transcended almost immediately after beating back the spectral horde. Stygia, both the city and the society, collapsed and the Yellow Springs retreated after taking damage far beyond their worst-case expectations. Complicating matters, the oldest and most powerful of the Risen, Persephone, attempted to flee into the Skinlands just as the storm hit; her escape attempt caused the Shroud to resonate, flinging thousands of spirits out of the Underworld and into the Skinlands. Some became Risen themselves, while others just wandered the Skinlands in spirit form. This accounts for large numbers of Risen and ghosts later encountered by the Imbued and the Orpheus Group.
The fury of the storm was so great that it also also had the unfortunate side effect of awakening many powerful beings who were sleeping until the force of the storm jolted them. The most destructive of these was the mother of the Malfeans, Grandmother. Hungry, she began to set plans into motion to feed, the first action of which was to fling her own offspring into the Maelstrom, making the once all-powerful Malfeans completely helpless. The Fallen were also awakened by the Maelstrom, and began to escape from the Abyss and resume activities of their own. Osiris awoke from his millennia-long slumber over Amenti. He then proceeded to make those of the Children of Osiris, who were vampires, that refrained from consuming human blood and retained recognizably human values into humans once more as a reward for their faithfulness. This includes all of the concomitant joys and limitations. In the aftermath, the old Spell of Life lost its potency and no longer works. Osiris delivers a new Spell of Life. The new spell is without flaw and it is far more powerful than its predecessor. This is used to create the new more powerful improved Undying. Osiris then merged into the Web of Faith.
All through the tragedy and struggles, the Underworld was now enveloped in a storm of indescribable fury which continued until the end of the world.
This violent event occured in what was supposed to be the final book for the game Wraith: The Oblivion, and although it was deemed the "Final Maelstrom", the continuation of the timeline proposed by the Onyx Path Publishing means that these events might not be entirely considered canon any longer.