Hearthpwn

Intro

The quest mage before the quests. Mostly freeze mage with a minimal amount of minions and maximum amount of patience! 

Gameplay

Staying alive is your main objective. That and controlling the board. Most of your time should be spent thinking ahead. Anticipating your opponent's turns (Lich King, Tirion, Draconid Operative, etc.) allowing you to drop a doomsayer the turn before to screw up their gameplan and stalling until you have your combo. In general: Stall the game with Doomsayer, Frost Nova, Volcanic Potion and Blizzard.

When you're not stalling, draw cards until you have 2 x Sorcerer's Apprentices, 2 x Molten Reflection, a less-than-5 mana spell card and Antonidas in your hand, then drop Emperor Thaurissan. Next turn, go bananas with unlimited fireballs (exodia!) 

Substitutes

There aren't many cards you can substitute, but you could switch Volcanic Potion with Explosive Sheep. Might be handier against secret/quest mages with their damn counter spells. Even kills their own minions if they happen to play explosive runes when you drop your sheep. Bloodmage Thalnos also loses value if you switch to the sheep, so you can also sub him with Novice Engineer if you don't have the dust. Though Bloodmage Thalnos empower all your AoE spells, he's not played in too many decks. If you don't like playing rogue or other decks with heavy draw at all, it is probably not worth crafting him altogether.

There is also some wiggle room with Echo of Medivh and Cabalist's Tome. Cheaper alternatives that give you some pseudo draw are Duplicate, Shimmering Tempest, Babbling Book or Shifting Scroll.