This deck provides good board presence in the early game. Don't be afraid to use a penguin on turn 1 with your voidwalker or flame imp instead of playing solitaire waiting for a wombo combo. Turn 1: Flame Imp + Coin + Voodoo + Happy Ghoul + Penguin --> always feels good.
Deck is peppered with synergy for Drakkari Enchanter, who provides a big body against 1/1 tokens and makes Shrieking Shoom, Cobalt Scalebane, Dreadlord, and Lich King that much better.
There is synergy between Glinda and the Happy Ghoul, Arcane Tyrant, Sea Giant, and Penguin.
Rin makes an appearance because of a Taunt body, an additional 5 cost spell to trigger the Arcane Tyrant Tempo play, the Galinda wombo combo, and because Rin can be a win condition all alone.