Academic Espionage and Tess Greymane created a lot of problems for Hearthstone players last season. This time they're back, with even more tools to play with, such as Underbelly Fence, Vendetta, and the one and only Heistbaron Togwaggle.
All three cards synergize well with the thief mechanics of this archetype, so bringing chaos to the battlefield is even easier.
Another addition from Rise of Shadows plays a very important role: Hecklebot. This taunt minion removes combo pieces from your opponent's deck so that they can't OTK you or summon a powerful battlecry minion like Kalecgos.