The main mode of Nemesis: Aftermath is Epilogue Mode, a short (45-60 minute) 5-turn game played after a regular game. As this epilogue begins, an unspecified amount of time has passed since the events that took place in the base game of Nemesis. Players use characters (who were not part of the base game) to enter the Nemesis to investigate. The ship bears many scars from its previous travails, so remnants of your previous playthrough will have effects on your epilogue playthrough.
An epilogue game is much shorter than a regular Nemesis game, but it is more difficult and offers a very dynamic playing experience. Instead of objectives, players must deal with seemingly simple personal requirements, while trying to work together to tackle various alerts. Additionally, players who pursue more selfish interests may accept lucrative offers. The players also use the additional Shuttle board, which represents a new small ship (moored at the Nemesis) consisting of 4 additional room slots. The Nemesis: Aftermath expansion also adds 4 new rooms.
You can play the epilogue game with fewer players than the number who actually participated in the regular game.
Nemesis: Aftermath adds an attribute card for each character (both from the base game and the expansion). Trait cards provide specific advantages and disadvantages during the game. The trait card is placed face up next to the character board, and its rule applies for the rest of the game.
Nemesis: Aftermath adds 5 new characters to the game. When players choose their character, the character draft card they select allows them to choose either the base game or the Aftermath character of a chosen color. For example, the red Aftermath character (the convict) can replace the red base game character (the soldier). After choosing their character, each player keeps their selected draft card, preventing other players from having the option to choose the other character of the same color. The two red characters (the convict and the soldier) can never be together in the same game. The Aftermath characters are very different from the base game characters.