This is a simple Magic the Gathering card combo for Standard that forces your opponent to attack into your wall so you can kill their creature with your Assassin.
Here’s how it works:
Virulent Swipe is another option, should you not have your Royal Assassin out yet. Simply cast Swipe on your Wall when it blocks. This combo worked particularly well with M11’s Prized Unicorn and Scars of Mirrodin’s Infiltration Lens.