The archetypal Assassin's Creed moment goes like this: you infiltrate a historically significant building, stab some historically significant villain, listen to a dying speech that lasts a surprisingly long time thanks to the technomagic of the Animus, and then you run the heck away. The running away is important, because you don't want to get caught and forcibly desynchronized.
Important enough that it's been interpreted as a new mechanic in the Assassin's Creed x Magic: The Gathering crossover called Freerunning, which lets you play certain cards for less if one of your assassin or commander cards caused damage that turn. Whether you're leaping off Notre-Dame or Big Ben you ought to be doing it at top speed, and Magic's crossover set simulates that by boosting your tempo with reduced-cost cards., make too much sense not to bring back.
Historic cards are returning as well. Any legendary, artifact, or saga counts as a historic card, but having other cards that care about that designation is rare. Again, it makes sense to bring the designation back into prominence for Assassin's Creed, a series of games that may play fast and loose with the facts but always evoke the essence of their historical settings.
The card we're previewing from the set is one that interacts with historic cards. The Desynchronization card returns nonland permanents to their owner's hand, unless they're historic. You won't be able to get rid of Leonardo da Vinci , or your opponent's, but anyone that doesn't belong will get blipped away like they've stabbed too many innocents or otherwise broken the simulation of history.