The Abyss

Beside the land, in the darkest pits, there dwell ancient things; some mere animals, some only definable as godlike. Massive bioluminescent shapes twist madly through the inky black, ancient intellects of unfathomable desires, cities built of slimy stones in the dark waters, ancient elemental terrors of crushing pressure and churning magma. Welcome to The Abyss. Crux's oceans are deep, deeper than Earth's by many times, and in those depths, in the deepest places beneath the shining reefs of the Ocean of Kanoqt, is The Abyss; the domain of darkness and primal fear. The few sentient beings that bring knowledge of these dark depths are commonly the most powerful sorcerers and magic-users, and Krakens.

Creatures insignificantly small and incomprehensibly large swim through the darkness of this realm, and those aforementioned 'godlike' beings are here too. While this place is the domain of the Krakens and Shuliak, it is unknown if Shuliak is even concerned with the inhabitants of the Abyss. The Abyss gives way to land at about 30 kilometers down, and starts at 11 kilometers below surface.

History
The Abyss has no known history, as no one can survive in its conditions.

Normal (but oversized and rather horrific) sea life
Utterly gigantic fish and other such creatures dwell in The Abyss, adapted to enormous sizes to make up for the intense pressure i.e. abyssal gigantism; these creatures commonly die and surface, giving many fishermen frights of their life as they find fifty meter long serpent-shark monsters half-decayed into shaggy faux-tentacled masses of flesh in their nets. Otherwise, they're genuinely terrifying, given how different from terrestrial and even near-surface ocean life these lifeforms are. However, as many of these creatures are lethargic to prevent the waste of nutrients through excess movement, these creatures commonly are simple filter-feeders and passive predators.

Though, there are a rare few species down here that are truly horrifying predators, having some adaptation to keep them from expending too much energy, allowing them to properly hunt instead of simply wait in ambush; these monsters are what fishermen, and fish-men, should fear. Some... some may be able to rise up from the hadopelagic pressure. The sheer horror of such a voracious, and excessively well proportioned, carnivore puts fear in the hearts of even the bravest of men.

Magical Hadopelagic Sea Life
While rarer than mundane sea life, the magical sea life are much worse. Considering many have the capability to survive the changes in pressure one experiences during ascension in the ocean, they are truly what inspire the folklore of sea monsters; titanic leviathans of piscine might combined with unnatural speed and strength. Some grow strong enough to rival the Krakens in might, and become a threat to the world around them, sometimes culminating in a force of Krakens having to destroy the creatures.

Godlike Beasts of the Sea
These are immensely powerful monsters, so strong that they could easily gulp a Kraken down whole. Horrific beyond mortal ken, these sea-gods are living incarnations of the fears of the sea, thalassophobia made manifest. When one wakes, the world quivers in fear. These creatures were commonly recruited by Shuliak during the Year of Wrath, and many were given positions of power when they and their liege-lord were banished back to the Spheres Beyond. Those that still sleep in the dark, those horrific demonic things that predate mortality yet still dream in the dark waters... they are world-shattering threats. If they, collectively, were to awaken, the World would be destroyed in seconds; unless they happen to be benevolent or simply interested in what has transpired on Crux during their sleep, in which case they, even then, might cause untold destruction by their mere presence.

Sentient Species
There are few known intelligent species in the Abyss other than the Krakens and the God-Things, as the Abyss is deadly to terrestrial and non-Abyss life and likewise the surface and higher oceans are deadly to the Abyssals. Krakens are postal workers when communication between the two worlds is required.