The Abyss

The Abyss is the elemental hell of water. Those that have seen this diabolic plane have described it as a shoreline of mires and bogs that changes as the waters deepen and change from fresh to brine. Pilgrims who journey to the Abyss find that it is roughly divided into four regions, each deeper, darker and more perilous than the last, until the traveler passes from the deepest point of the Abyss into the Void itself.
The first zone of the Abyss is the Edgewater, a broad coastline of freshwater swamps, ponds, streams, rivers, salt marshes, and estuaries. The Edgewater is the shallowest, least hazardous region of the Abyss. It is a region inhabited by minor fiends and demonic undead. The most common fiends in this region are the Drowners, such as the rusalki, kappa, and vodyanoi, who dwell in rivers and millponds, where they drag down their unsuspecting victims to watery graves. Other fiends of the Edgewater are the black annis, child-eating swamp hag, tikoloshe voracious sexual predators, and mbulu, amphibious tricksters and impersonators.
The Far Fathoms are deep, gloomy lake-waters inhabited by fresh-water demons such as kelpies, aquatic shapeshifters that change from human to horse form, the nautical cities of serpentine water nagas, and the massive, frog-like wahwee that cause droughts and floods and bunyips, huge, seal-like, marine predators. There are even stranger denizens in the Far Fathoms, such as Munuane the demonic fisherman, whose eyes are in is knees. Munuane although slow-witted is a skilled ferryman and peerless archer, whose arrows not only target fish the often mark cadavers of his human prey. Ahuizotl is another unique fiend of the Far Fathoms. It believes all the fish of the high mountain lakes are its property and as such it swims out of the Abyss to crush the boats of “thieving” fisherman. Besides a dark shape beneath the waves, there is no description of Ahuizotl, for none who have ever truly seen the fiend have survived to play witness.
The Utmost Dark is a gloomy, brackish span of water. This is region is the abode of more lethal marine demons. It is the habitat of the merrow, demonic nymphs, whose seductive, haunting music rises up from the waves, siryns whose song lures sailors to their deaths, and the Ponaturi, evil water fairies that drag ocean swimmers beneath the waves, but are destroyed instantly by sunlight (which is totally absent in the Utmost Dark). Larger fiends also dwell in the Utmost Dark, such as Scylla, the sea serpent, and Charybdis, the floating island, who work in conjunction to sink ships in the Shadowlands but then return to the Utmost Dark. Further beneath the waves swims massive, squid-like kraken and other terrors of the deep.
The furthest, most foul and hazardous region of the Abyss is the Mare Tenebrosum, the Sea of Darkness. This is a region of black water is locked in utter blackness because of it directly borders the Void. It is a shadowy sea where the ghosts of lost ships and seamen sail forever in perpetual darkness. The Mare Tenebrosum has been known to leech into the oceans of the mortal realms, but is not marked on any charts and may even move slowly over the surface of the waters following the track of great ocean currents. Seamen never know that they have entered the Sea Darkness until night has fallen and the sea becomes mysteriously calm, no matter how rough it may have been before the sun went down. There is no moon or stars and the heavens are obscured by solid black cloud.
Then there is an agonized hail out of the darkness: the kind of choking, despairing cry that a swimmer might utter in the moment before drowning. This is soon followed by other sounds, voices: the savage yells of men fighting for their lives; the screams of women and children as a ship sinks beneath the waves; orders bellowed in the language of every seafaring nation. The sails of a full-rigged ship seem to glimmer through the darkness, or the oars of a war galley or the bows of frigates churn the water into foam. At last all the sounds coalesce into a bloodcurdling wailing, as ghostly ships loom up and disappear before the bow of the intruding craft. When a vessel might drift becalmed in the Mare Tenebrosum the sights and sounds are so appalling that dawn might find her crew in a condition of near insanity. Other vessels never leave the shadowy reaches of the Sea of Darkness but are instead drawn through it into the Abyss. These ghost ships then float out into the Utmost Dark to haunt the waters of the Abyss. What types of demons dwell in the Mare Tenebrosum remains unknown for none have successfully explored this region. It is known only that the most potent and virulent demons, such as the Leviathan, dwell here. Fiends so horrible they are never seen yet their legends are undying.