REZ - Lithtech Game Engine Resource File is a different type of file extension in which you can use for your benefit. It is a very common and well known resource file used in most first person shooter gamers. These games come from Lithtech gaming engine. This file extension, which is very useful, contains maps, music, textures, and many other objects that you can use when playing this game. Some of the supported games are Aliens vs Predator and Blood II Condemned 2. Sierra Entertainment Die Hard, and Nakatomi Plaza Jarhead are a couple of other games that can be used with Lithtech resource files. You will also be able to change the REZ files using Dragon UnPacker, or even Game Extractor. You can also use lithrex.exe to extract any file that you need to that has to do with the game. It was developed by Monolith Productions as well as Microsoft.