Aftershock for Quake, or simply Aftershock, is a commercial add-on for Quake developed by HeadGames Publishing, Inc. and published by GT Interactive. The add-on was released on November 10, 1996.
Besides adding custom levels, this add-on also includes a .PAK file manager named XPAK as an attempt to promote a more secure method of editing game files. A beta version of THRED, a Quake map editor made by Jim Lowell and John Mavor, is included. THRED was unsupported on the Aftershock disk due to being a pre-public beta release. This editor was HeadGame's secret weapon and reduced competition against rival developers. While commercialized heavily prior to the release of this commercial add-on, Mavor was paid to not release the editor so that Aftershock for Quake would have a technological advantage over other companies.
The main text file for the game includes various tips for the Weapons and Enemies of the game. There is also a small portion dedicated to the most common Console Commands. The text file also manages to compile a complete list of Secrets for the Base Game.