From the get-go, we have known Conspiracy is rather different than past summer supplemental products. Unlike Planechase and Archenemy, Conspiracy isn't sold in preconstructed decks - rather, it's a booster-pack-based, randomized set made to be drafted by six to eight players.
And typically, the summer supplements have no story continuity and don't take place on any one world or in any one time period; Commander legends, for example, are from many different planes in their backstories. So it's only fitting that Conspiracy should have a real setting and storyline just to be contrary. When sariadog asked Mark Rosewater on his Tumblr blog, "On which plane (if any) does Conspiracy take place?" Rosewater answered:
While I am not yet at liberty to tell which plane, I will say that the set does take place on a specific plane.
Based on the artwork we've seen so far, many have been quick to speculate that the said plane is either Ravnica or Innistrad. However, this doesn't quite fit - Magister of Worth, for example, has neither an Orzhov sigil nor an Avacynian collar, something she would need to identify herself as a white and black Angel on those respective planes. So if Conspiracy is missing the visual cues for both of these well-loved settings, where could it be?
The prevailing theory is it's someplace never-before-seen in a set. A couple of fitting planes that are at least known about are Fiora, the home plane of Dack Fayden, which is based on Renaissance Italy and thus full of political intrigue; and the sophisticated and opulent, unnamed home of Sydri, Galvanic Genius.
Where do you think Conspiracy is taking place? Let me know in the comments.