Hearthpwn

For the current meta, especially when heavy-late game priests and druids devastate through enemies, this deck beautifully crushes them.

Cannot provide an extremely detailed gameplay but here goes a few secrets;

-Generally stall the early game, do not over-play minions. Try to never let cards in your hand go below 5 or 4 unless an extreme aggro appears. Pretty killer against common aggros, generally do not even need Frost Lich Jaina.

-Why do some odd cards exist like Bonemare in a mage deck?
1.Yogg-Saron, Hope's End: This card is either a last-chance gamechanger or a critical helper against hopeless situations. Against Raza-Kazakus priest, with the new spells added, Yogg generally ended up turning the game around. Secrets are there for him but you can choose whatever secret you wish.

2.Bonemare: Since this deck has a more minion-focus, this gem can save your frozen tush just before an Ice Block trigger. Or it can create a huge finisher/lifesteal elemental after you turn your hero to the crazy sword holding blue mage. Best used with 10/10 Pyros if you can keep it on board.

3.Vicious Fledgling: This card, imho, was unbelievably extremely hardcore OVERPOWERED the first time it appeared and it still is. Think about it. Direct target for any kind of minion on board because it's a gigantic threat. Especially when used with Bonemare, instant lethal with a bit of luck. Also awesome for averting damage or spells. An imminent threat, finisher potential or attack magnet. No-brainer in my case.

4.Primordial Drake.  The frost lich is all well and good. Elemental Lifesteal is also great but you can easily gain profit and reach to 30 life really quick and after that lifesteal generally means nothing. And in the case of elementals, except from Ozruk, no good taunt exists. Anomalus also works good but still no taunt. On the other hand this dragon deals good enough damage to the board to keep it controlled while both providing a possible hero power/water elemental combo and a good taunt body. 

I tried to keep this deck minion-oriented while not losing spell numbers for a Yogg-a-destruction chances. Thus Babbling Book, Shimmering Tempest and Cabalist's Tome. The secrets are also oriented in a way to both provide a spell and a minion. Minions are good in the current meta.

Good cards to keep at mulligan, respectively; Babbling Book, Mana Wyrm, Pyros, Ice Walker, Shimmering Tempest and other low-costs. Try to keep servants as long as you can but when you need a good body, just go ahead and play them. There are also some board controllers like cone of cold or a huge flamestrike.

Other than aggro decks, the playstyle focuses mainly on controlling the board with spells until mid-late game. Providing backup with a few minions in mid and kicking butt with your big minions-yoggs and bonemares at the end while still keeping the board clear with the drake and flamestrike...

Basically this. Always of course open to suggestions and changes.

Ozruk could replace Primordial Drake
If you feel too aggro, The Lich King could replace Fire Fly or any other low-cost.
Any secret could replace any secret