Compiled from Rob Kuntz's various blogs, fan pages, and his new publishing company, TLB Games:
Kalibruhn is the campaign setting created by Rob Kuntz in 1974, having grown it organically from a setting shared with Gary Gygax, his co-Dungeon Master. Both Gygax and Kuntz famously used the map from the game "Outdoor Survival" as a wilderness map for their shared campaign world. Eventually both would create their own distinct settings: Greyhawk and Kalibruhn.
The original Dungeons & Dragons Supplement 5 was intended to be KALIBRUHN, but it never reached print. Kuntz has continued to release material for this setting, including "The El Raja Key Archive."