If you want to know how to beat Heroic Karazhan The Crone the Opera Wing then the video, deck list and notes in this post will take you through it and make it really easy for you.
By completing The Crone on normal mode you unlock the following cards:
You get to choose to give your minions charge or taunt depending on which side to Dorothy you place them. You need to beat The Crone before turn 8 ideally as she casts Twisting Nether and clears the board. The video below takes you through how to complete this boss.
Deck List for Heroic Karazhan The Crone the Opera Wing
Priest Class Cards
2 x Flash Heal
2 x Inner Fire
2 x Light of the Naaru
2 x Power Word: Shield
2 x Northshire Cleric
2 x Divine Spirit
2 x Resurrect
2 x Lightwell
2 x Velen’s Chosen
2 x Shadow Madness
2 x Holy Champion
2 x Priest of the Feast
2 x Darkshire Alchemist
2 x Cabal Shadow Priest
2 x Temple Enforcer