|Released||July 28, 2007|
|Updated||May 14, 2008 (0.6.9A)|
|Platforms||Windows, Linux, Mac|
|Game Length||10-20 hours|
|Official site of Incursion|
Incursion: Halls of the Goblin King is a freeware roguelike game based on (but not strictly adherant to) the mechanics of the d20 system made available under the Open Game License by Wizards of the Coast.
According to the developer, Incursion: Halls of the Goblin King is "a promo game for the upcoming roguelike epic Incursion: Return of the Forsaken", which will feature overland map, multiple dungeons, towns, more prestige classes and other features. At moment, Incursion features only a single multilevel dungeon. Return of the Forsaken is slated for release in 2011.
The developer has stated that the source code will be released at some point in the future.
The great tech doc about the game is provided here. It had to be useful in roguelike development.