It's often that you find an expansion for a board game that also counts as a stand-alone game ("expanshalone" is what I remember calling something like that back in the day). What you don't quite see so often is an RPG that's a stand-alone expansion. But that's what we have here. Mutant: Elysium is the 3rd of the Mutant: Year Zero RPG expansions, but while it's an expansion, it's also a stand-alone game on its own. The game is up on Kickstarter now.
From the campaign:
This is the third major expansion to Mutant: Year Zero, the award-winning postapocalyptic tabletop roleplaying game by Free League Publishing.
But Mutant: Elysium is no mere supplement - it stands on its own and can be played as a complete game in its own right. Get ready for the final fall of humanity!
Note:Mutant: Elysium is a game that tackles some sensitive subject matters. In the game, players represent the ruling Houses that control the Elysium I enclave. The players start the game in positions of power, and a part of the challenge of the game is how to handle that authority when society starts to unravel around them. This game is does explore potentially sensitive themes, but it's not trying to make a political point.
The Kickstarter is at more than 5x its funding goal with 22 days left to go.