Step one: mulligan until you have at least two of the twelve merchants in hand.
Step two: use the merchants to fetch Jarrall Iceheart
from the market.
Step three: use Permafrost
and blocking with Merchants to survive until you have seven mana.
Step four: play Jarrall, play Savagery on Jarrall, use his Killer attack one of your opponent's creatures. Reveal The Witching Hour
, which should still cost 16-18 power.
Step five: watch as Jarrall does 16-18 Overwhelm damage to every creature your opponent controls, dealing all of the excess to your opponent's face. Laugh maniacally as they go -80 if they have a full board.