Welcome to New Atlantis, city of a thousand demiplanes, a thousand ships, and a thousand thousand stories!
This is a crapsack world with a few bright spots: one of the brightest is the recently invented drug Delirium, or 'Lyrium as it's known on the streets. This drug makes you swooningly happy for a few hours before you fall into a deep and pleasant sleep. Another bright spot is the invention of a cheap, easy way to bind elemental fire in tiny amounts to common iron (as a third level arcane spell) for a year and a day, causing the dawn of the Crapsack Steampunk.
As the story opens, the Fire Hobgoblins are planning their Third Annual Invasion of Atlantis. It used to be that Atlantis held competitions to route the hobgoblin tribes...until the hobgoblins discovered how to create Mech Armor. Now the tables are turned, as the less-heat-tolerant Atlanteans race to gain an edge against the technologically superior hobgoblins.
Interesting points of mechanical play:
Drugs. Atlantis is the drug capital of the world, offering a cocktail suitable for practically any purpose...including adventure.
Mech Armor. Casters are advised to extreme caution.
Supermonks: A homebrew base class
Psychic Dragons: Another homebrew class.
Pocket Dimensions: Genesis is a fifth level spell/power. Pocket dimensions are practically everywhere.
No Tome of Battle. Sorry.
No Magic Item Compendium.