The Abyssal Fleet is an unofficial faction not endorsed or supported by Games Workshop but with its own unofficial battletome and therefore page

Hidden in the depths of the Shyishian Sea there is an Abyss, a Prison forged by the hand of the Lord of Death himself. No mere Stormvault of Sigmar able to be cracked by a savvy enough looter the seal on this ancient vault was tied to the very power of Nagash himself. By the hand of Teclis that power waned, only for the briefest moment but as it did a crack tore through the seabed and the Maelstrom unleashed…

The Denizens of the Abyss now rise once more, those who in life knew loyalty to no-one, those bound to the wilds and abandon of the raging seas of the realm. Even in death they defied a god who lay claim to their souls, reaving and ravaging the Temples of Nagash as who sought to break their rebellious wills.

Pirates, Privateers, Deserters, they may have been known by many names in life, perhaps even to their own mind they were the heroes of the tale. But the sea will stand no such lie, the Maelstrom has weighed their souls and found the darkness within. Though they have escaped the Abyss its tendrils reach ever outward seeking to reclaim its prisoners.

There is a debt to be paid, but Pirates know a debt can be… transferred….