Cheap Dragoncaster Askaara Priest Deck (Heroic Mode) for Galakrond's Awakening

With this deck you should look to get onto the board as quickly as possible. Aside from Arcane Breath, the boss has no way of immediately interacting with the board aside from randomly-generated spells, making it easy to develop a big minion early using Power Word: Shield and Velen's Chosen.

In the mid game, you can take full advantage of the Dragons used by the boss and use Dragonmaw Poacher and Dragonslayer to neutralise the boss' tempo advantage.

Once you have assembled additional Divine Spirit and Inner Fire combo pieces, you can build yourself a large minion to start bursting down the boss. The only card the boss has that can deal with this is Malygos, Aspect of Magic, which can generate a Polymorph, making this strategy relatively safe if the card has already been played.