Hakkar Druid is the new Combo Druid deck created in Rastakhan’s Rumble. It’s a deck that focuses solely on the combo, with no other win condition whatsoever.
The goal is to cycle through your entire deck as quickly as possible, then drop Hakkar, the Soulflayer and kill it off. Once you do, you switch decks with your opponent thanks to King Togwaggle and force them to draw with Naturalize. The damage ramps up very quickly. Assuming you took the first 3 points of damage, even with just a single Naturalize your opponent will take nearly 50 damage in total.