A new trailer for The Witcher 3: Wild Hunt has been released, and it is titled story recap. However it doesn’t actually explain many of the major events that have led to this point in the story, and to be fair I don’t think any trailer adequately could. Sure, you have the general overall plot of the Geralt being a Witcher, and the Wild Hunt that comes for him, but outside of that there are a lot of branching paths that lead to different events.
Take for example The Witcher II: Assassins Of Kings which has 16 different endings alone, all of them based on decisions you may or may not make in the world when interacting with the various parties. That makes a story recap trailer hard enough to do since players will have come to different conclusions. Also that number of endings is nothing compared to how many Witcher III will have, with a total of 36 confirmed by the developers. Still, as a general history on the Witchers the trailer is a little educational.