Although there are an uncounted legion of Demon Worlds, on Algol "The Seven Rim Demon Worlds" refers to the Demon Worlds that comprise the shortest path through the Abyss to the Deeper Demon Worlds.
ABODE OF KEDEROTH OF THE EVER SEEPING EYE
The Demon World OGGUTT is a toroid shaped world, its atmosphere suffused with massive ragged clouds of semi-living gaseous colonies that emit blude, green and ultraviolet light. The regions of OGGUTT that lie withing the central, or "hole" portion of the world are a torrid jungles of acidic and poisonous, animate, yellow-green vegetation; while the outer regions of the world are a frozen wasteland of towering glowing spires of radioactive ice.
ABODE OF HOLOK-KOZAR BEARER OF THE CROWN OF DEATH
The Demon World ZAIYAAT is an endless, bottomless sea of slimy, viscous, phosphorescent, green liquid; floating fragments of unthinkably massive, fossilized or decaying abominations serve as islands. The black, city sized Temple Barge of the Worm Sibyls haunts this world.
ABODE OF EZETHOTIK THE PENETRATING BEAM
An endless subterranean maze of crumbling ruined catacombs and palaces, suffused with sulfurous and poisonous gases spewing from chemical geysers and punctuated by occasional pits of squirming larvae.
ABODE OF PHAR-HOAZ THE BURNING LORD
A desert of hot grit, embers and brass, scoured by unending wind and fire storms. Towering colossi in the form of palaces atop elongated legs stalk across the writhing dunes.
ABODE OF AZAKAZIEL THE SLITHERING QUEEN
A neverending labyrinth of deformed mirrors, haunted by hallucinations and the echoes of chimes, cymbals and bangles.
ABODE OF THE UNKNOWN ONE
A region of swirling glowing black and red breathable gases filled with hundreds of planetoids. Many petty minor demon lords have their holdings on one of these planetoids. It is said that THE UNKNOWN ONE uses these demons lords as pawns in it's entertainments.
ABODE OF XILTAZIAK THE FLUTTERING MALICE
The Demon World of URUHKHT is comprised of a planet-sized cubical cavity in a mass of slightly radioactive, luminous silvery-blue metal. All six faces are covered with sprawling cities, pavings and ruins of lead and basalt while a painfully bright white luminous sphere lies in the center of the cavity. Many of the more mercantile varieties of demon coagulate here.