1. The References
Innistrad is a beloved plane with beloved cards and Eldritch Moon might be the last set on Innistrad as we know it. Consequently, it's got a lot of callbacks to earlier cards in the set. From the reprint "Prey Upon" with new art altered slightly by the Eldrazi to Tree of Redemption's final fate as Tree of Perdition you physically see how Innistrad has become not just besieged as it was in Dark Ascension, but utterly corrupted.
