This combo is aiming to make your opponent into Ragnaros, steal their hero power, and kill them with it. The deck is built like Mecha'thun Warlock to draw ASAP, and because 1 drop minions can be useful to throw out of your hand if you need more minions for Plague of Flames to kill.
The best way to trigger the combo is to have no other minions in your hand but Majordomo Executus, Shadow Hunter Vol'jin, and Grizzled Wizard with the spells Plague of Flames and Treachery. Emperor discounts or Quest discounts are needed for the combo.
Combo: Play Grizzled Wizard, Shadow Hunter Vol'jin the wizard to pull out Majordomo, Plague of Flames to kill the Majordomo, turning your opponent into Ragnaros. Then you play Grizzled Wizard again to steal the Ragnaros Hero power to deal 8 damage to the face.
There are some games you cannot kill your opponent, so in those situations, you can still turn your opponent into Ragnaros, capping them at 8 hp, AND PERMANENTLY steal their hero power. In order to do this, play Grizzled Wizard before killing Majordomo, and at the end of the turn, the hero powers will flip, giving you the Ragnaros hero power.
For more info on this deck, feel free to check out the video below!