Barrens Clown Priest

Overlord Runthak + Gift of Luminance when Carnival Clown is your hand to buff it.

Use Scrapyard Colossus to corrupt your Carnival Clown obviously.

The gameplan is just to survive until you can pull the combo off.

Alexstrasza the Life-Binder is a potential finisher and Shadowform is just a flexible ping card to kill minions and chip away at the enemy's face bringing you closer to lethal.