The best common card in the new expansion is definitely EVIL Recruiter, which creates a 5/5 Demon after sacrificing a lackey. This card alone is so powerful that it has become the foundation for the brand-new Zoolock archetype.
The list also includes two copies of EVIL Cable Rat and EVIL Genius, which together can produce up to six lackeys. They are quite strong on their own, but with the help of EVIL Recruiter, you can have a 3/3 and a 5/5 minion on turn three, and right now, nothing can beat that swing.
If the deck is too expensive for you, then you can exclude The Soularium and Leeroy Jenkins, as the deck is still super powerful even without those legendaries.