A Mass Effect 3: Citadel FAQ has answered a couple of questions about the right time to play the content and how it will progressively unlock through the main story; this information contains some minor spoilers, so don’t read on if you haven’t completed Mass Effect 3.
In a post on the BioWare blog, the developer said the content does not change the ending, although it can add to your Galactic Readiness. Citadel unlocks any time after you’ve stopped the Cerberus coup attempt, and can be played any time before you attack Cronos Station, which triggers the final missions of the game and locks the player in for the duration. However, it can also be accessed in the end game state available after the final mission.
As previously detailed, the DLC allows players to connect with old friends one last time – but these friends will only appear on the Citadel after you’ve completed their missions and follow-up conversations in the main game.
BioWare gave one example; Jack appears after completing Grissom Academy and talking to here in Purgatory. Players who haven’t yet done all the other missions will see the character content unlock slowly as they progress.
Mass Effect 3 released in early March 2012, making it almost a full year old. Citadel arrives on March 5 (or later, depending on when your local PlayStation Network updates) and will be its final piece of story DLC, tying into an upcoming comic series. It will set you back $15 on PlayStation 3 and 1200 MS or BioWare Points on Xbox 360 and PC respectively.
BioWare has also continued to support Mass Effect 3′s multiplayer mode with frequent, free expansions, culminating in last week’s Reckoning pack.