The known islands and island clusters are:
Lindolah - A norse style dwarf and giant dominated land. The island itself is roughly circular and nearly 700 miles wide.
Toldoth - This island has another just off the southern coast named Asteroth. Together the islands barely stretch 400 miles from the northern most point to the southern. It is ruled over by a Hobgoblin.
Twin Islands - The Twin Islands each are a quarter moon shape, one to the northwest, the other southeast. A 20 mile dwarven bridge spans the gap between them. A planar gate resides on the southeastern island.
Oblivion - Contrary to the name, it isn't overly hostile. This is a cluster of 4 large islands with several smaller ones scattered in every direction. The name was given by humans who stumbled across tests being conducted by the gnomes who control the cluster.
Hingol - Another cluster of 4 large islands, this land is very mountainous. The architecture is largely oriental style, as is the society. Dwarves and the strange Mountain elves mine the mountains for precious metals and gems to trade.
Seven Isles of Fire - Aptly named. The planar barrier to the elemental plane of fire is thin here. Most of the land is barren, even giving way to the occasional permanent fire. Djinn and some elementals claim sections of the land.
Region of Insane Demonic Delights - This region is named so for the thin barrier to the lower planes. Many evils reside here, doing what they wish and causing mayhem and destruction. A beautiful weekend getaway.
Har' Dil' Flan - Illithids have used their immense power to dominate this land. No light shines and fire is quickly snuffed out. A constant downpour blankets the already swampy land. Mind Flayers walk upon the land, taking what they will.
Halder - Formerly a beautiful, untouched countryside, this wasted island is controlled by undead. A bastion of death stands as the only city. The Ebon Hold. A massive ziggurat made of an unnatural black stone.
Highlands of Sinetala - The highlands are much like a mesa, standing 500ft above the ocean, with cliffs as the only coastline. Swamps are scattered about from the tropical rains that commonly sweep the area. It is among the largest of the islands, stretching nearly 1000 miles at the furthest points. This land is one of the least hostile. Many cities dot the landscape.
Dorshire - Dorshire is the third largest island at roughly 600 miles long. This land is the most accepting of the many sentient races. The capital of Dorshire City has a mix of many creatures, including elves, orcs, and even the occasional ogre. Much of the established lore is related to this land.