PRE Step up: play Emperor Thaurissan hitting Jan'alai, the Dragonhawk and [Hearthstone Card ([Brann Bronzebeard/card] making a total 8 mana letting the combo work 

Pre Combo: if you plain to do the combo next turn you need to Doomsayer into Khadgar into Molten Reflection onto the Doomsayer making three Doomsayer's and then finally play Youthful Brewmasteronto Khadgar so then we can use him for the real combo. ( the reason we do this before the turn we combo is so the the three Doomsayer hopefully clear the board so that the combo summoning the four Ragnaros the Firelord for a 100%  chance to hit face for 32 damage) you can even play a card like blizzard or volcanic potion to lower the board size so the opponent can't  just trade into the 21 worth of stats to stop the 100% of the true combo 

THE COMBO: do the Pre Combo after the PRE Step up and then play Brann Bronzebeard into Khadgar into Jan'alai, the Dragonhawk to summon four Ragnaros the Firelord all to the face for 32 damage for the win