A few weeks ago, two of our party members got into a fight with an assassin. All we know so far is that the assassin is a doppelganger.
During the fight, the wizard used magic missile on the assassin, but the missiles were deflected and hit the other party member. The DM didn't explain how the assassin did so.
We're about to fight the doppelganger again, and we want to avoid this scenario if possible. What can deflect or redirect magic missiles?