These are the various dimensions throughout AbyssalCraft. All of them haven't been released yet, so expect them to become available over time.
The Abyssal Wasteland
This is the first layer of the Abyss, a place that's dark, green, and populated by the undead. Oblivionaire is said to be the one watching over this place, or his dragon, Asorah. Likely where Coralium originates from.
The Dreadlands
Previously a world of Abyssalnite, the Dreadlands got it's name when the Dread Plague was unleashed on it, killing all miners and corrupting the peaceful Abyssalnite Golems. The second layer of the Abyss holds lost souls of the living.
Omothol
A endless temple city built at the very edge of sanity. The Realm of J'zahar holds the only entrance to where The Great Old Ones dwell. The Gatekeeper is always watching, and nobody leaves the final layer of the Abyss alive.
The Dark Realm
To enter this realm you must fall into the void in Omothol.
(As of the latest update, one needs to defeat the gatekeeper to enter the Dark Realm)
Beneath Omothol lies the realm where the immortal souls of evil daemonic gods rest, awaiting their reincarnation. The Dark Realm is where living shadows are born, and the last place a living souls should ever visit, as they will face eternal suffering.