They are a reference to the Gramercy Riffs from the late 70's movie "The Warriors".
During a guest post on pockettactics.com, Sarah said that "Their name is a play on the Gramercy Riffs from cheesy cult classic The Warriors, which you should probably go watch now. Or not, it's terrible."
Rebuild 2 Edit
They debut as non-player-characters that appear and disappear from time to time helping with clearing out the "Zed " population nearby the Player's outpost, which impresses the local residents. They are around after starting a new city or starting a new game entirely.The Riffs aren't seen in pictures throughout the game nor is it known where they are hidden, but the player gets some descriptions about their appearance in occasional reports. Some interactions within the fort are described as well. As they wear fatigues the player may gets the impression that they are what is left of the Army in the post-apocalyptic world.
They are major rivals with the Last Judgement Gang, your rivals as well. There is a way to achieve an ending with their help which is to defeat the Last Judgement Gang at a chosen location.
Once this battle is completed, they seemingly disappear, or maybe they split or just left the city due to the fact that they think that the survivors can handle themselves the zombie situation and that there is nothing else to do for them since the Last Judgements have been defeated.
Rebuild 3 EditThey have returned in Rebuild 3 as an own faction, still in war with the Last Judgements. Here's their description during the kickstarter campaign for the third part:
"Ever seen the cult 70's movie The Warriors? Well I was a little drunk when I did (it helps) but afterward I couldn't get it out of my head. This faction is a play on the Gramercy Riffs, a badass gang of tall black karate dudes with mirrored shades. They value discipline, have a strict code of ethics and take a little too much joy in killing zombies with katanas and well-placed roundhouse kicks. You can hire them as mercenaries once you prove your honor."
Visit Rebuild 3: Gangs of Deadsville Wiki for further information.
Zombie Kill Squad (Rebuild 1) Edit
They weren't present yet, but similar events are telling about a "Zombie Kill Squad". They show up from time to time and clear out a few zeds on neighboring fields, just like the Riffs do. Though there is no report about a rivalry between the Last Judgement Gang and the Zombie kill squad.
According to their description reports, it's likely that they already have been inspired by the Gramercy Riffs.