Bioware has answered some questions concerning the upcoming Mass Effect 3 DLC titled Citadel. One of the key questions answered on the blog was when exactly the DLC content takes place in the Mass Effect 3 storyline.
In response, Bioware instructed, “You can play the Citadel DLC any time after stopping the Cerberus coup attempt on the Citadel and before beginning your attack on Cronos Station.”
The attack on the Cronos Station is of course the final mission of the game; however, it is obvious that you can also play the DLC after the mission ends, during the end game state.
Bioware has not listed which characters will be available for the DLC content but the characters that are in the mission will require you to complete their original missions before you can use them in the DLC.
Another important revelation is that the DLC will have no effect on the game’s ending. Furthermore, the game will be divided into two parts for the digital release on the Xbox but don’t worry it will be priced for one.