Hearthpwn

Concept

Control the game with board clears, discover effects and with N'Zoth, God of the Deep's menagerie while getting closer to complete the shattered pieces of C'Thun, the Shattered, your secondary win condition.

Mulligan

In general Cleric of An'she, Renew, Wandmaker, Venomous Scorpid and Palm Reading are good cards to start with but you should always think ahead with the upcoming battle in mind.

For example an early Raise Dead paired with Venomous Scorpid or Southsea Scoundrel are a good choice in Control matchups to generate early value with pressure (sometimes even keeping Mutanus the Devourer is worthwhile against Control) while Xyrella, Condemn, Hysteria, Apotheosis - only with playable minions of course - and sometimes even Lightshower Elemental are great defensive tools against Aggro/Midrange.

Tips & Tricks

Cleric of An'she: Extremely good card - similar effect like Thrive in the Shadows except it comes with a 1/2 body which is often a huge advantage. It can be buffed with Apotheosis or you can bring it back with Raise Dead to fish for more spells and get the shattered pieces of C'Thun, the Shattered easier.

Burning Blade Acolyte, Lightshower Elemental: Very strong Deathrattle minions. You can double their effects by summoning another copy with Gift of Luminance, Psyche Split or even with Initiation.

Update#1 - Replaced Insight x2 for the more proactive Southsea Scoundrel x2.
Update#2 - Replaced Archdruid Naralex for the more reliable Flightmaster Dungar.