NIF is a popular file format used by 3D games such as Morrowind, Oblivion, Civilization IV, and many more. The Blender NIF scripts enable you to read and write files that are compatible with these games in Blender.
In this release, Civilization IV .kf files can be exported, and a new option to prevent NiMaterialProperty optimization ("merging") on export has been added.
You can grab the latest version of the scripts here:
https://sourceforge.net/project/showfiles.php?group_id=149157&package_id=166219
For more documentation and help with the scripts, visit the wiki or the forum:
http://niftools.sourceforge.net/wiki/Blender
http://niftools.sourceforge.net/forum