Hearthpwn

Kill a bunch of combo pieces while spirit of the dead is out and then do the turbo omega combo with Holy Smite and Mind Blast! Lot's of flexibility on the set up. Can summon a variety of minions to enough damage and even summon copies of Prophet Velen and Malygos using Mirage Caller!

Can kill of your boys with Zerek's Cloning Gallery + Spirit Lash too. You can sometimes get lucky with Mass Hysteria.

Mulligan!

Against aggro:

You're going to want to keep Shadow Word: Pain, Radiant Elemental, and Spirit LashMass Hysteria.

Against slower decks you want a similar mulligan to aggro but you can be greedier with cards such as Shadow Visions.

Tech Options!

You're going to want to tweak this deck depending on how slow or fast the meta is. Some cards I recommend adding and playing around with are:

Spirit Lash More board clear

Mass Dispel More silence and draw

Shadow Word: Pain More small removal

Power Word: Shield Just more draw

Holy Water Easier to kill your minions and get more copies

Obsidian Statue Good stalling tool

Bloodmage Thalnos Good draw and thiccer spirit lashes

Lyra the Sunshard Good card to generate more spells

Gilded Gargoyle More mana for combo, probably not worth adding to the deck though

Shadow Essence I don't like this card, but it was run in the old version of this deck

Zilliax Good vs. aggro