FRIEND is a modification for Quake made by Jeff Epler. In 1996, this was one of the most requested features, leading to modifications such as this one. This modification comes with Rottweilers being modified to be friendly to the player, so it can be quickly tested in E1M1: the Slipgate Complex without much effort on the player's part. Friendly Monsters can be pushed as needed, plus will follow the player and protect them from any dangers they detect. Note that Monsters that are friendly to the player are always loyal, even if the player attacks them repeatedly.
By pressing impulse 250, the player can summon a Monster that travels with the player and fights alongside them. The summoned monster will usually be a Rottweiler, but can sometimes be a Grunt, and rarely the player will get a Fiend or Shambler. However, each usage of impulse 250 shall require 50 health from the player. Spawning against a wall will not work, there needs to be a relatively small amount of room (the size of a grenade). Note the health penalty shall happen regardless if the player gets a Monster or not.
Monsters also change their colors to reflect their owner, though this does not work in Deathmatch. Impulse 250 Monsters work in Deathmatch games, though there can be various errors, which the author didn't have time to fix.
To install this modification, the player must use a .PAT file with PATCH. However, there is a custom .QC file that is needed for this file to run called llsubs.qc. As such is not included with the .PAT file, and the installation can not complete without the custom file, this means that this modification is unable to be installed.