Step 1: play Luna's Pocket Galaxy and hit any 3 of the following 4 cards (Brann Bronzebeard, Cloud Prince, Zola the Gorgon, Leyline Manipulator) or alternatively just the two most expensive cards of Cloud Prince and Leyline Manipulator. 

Step 2: set up a Secret. Obviously Ice Block is ideal. Or keep a 0 mana secret you get off of Ancient Mysteries.

Step 3: play the following combo: 

Brann Bronzebeard + Cloud Prince (dealing 12 damage to the face) + Zola (adding x2 Cloud Prince to hand) + Leyline Manipulator (reducing the cost of x2 Cloud Prince to 1 mana each) + Cloud Prince copy #1 (dealing 12 damage to the face) + Cloud Prince copy #2 (dealing 12 damage to the face)

If successful, this combo deals 36 damage to the face in a single turn, potentially for as little as 6 mana if you hit all 4 pieces with Galaxy. However even a partial combo can still deal 24 damage from hand.

Of course there's lots of ways you can spin this combo. If she gets discounted, a 1-mana Barista is the same as a 1-mana Zola the Gorgon. If you can't draw Galaxy in time, you can generate a bunch of copies of Cloud Prince with Baleful Banker and shuffle them into the deck and THEN play Galaxy. Or you can combine Brann with Cloud Prince for a 12 damage battlecry plus things like Zephrys or Siamat or DQ Alex to help find surprise lethals.

There's lots of fun ways you can go about it, so be sure to experiment and keep an open mind!

Zephrys the Great: Pretty self-explanatory. An incredibly versatile card that provides a lot of utility. Useful for fending off enemy aggression or to look for that final bit of damage for lethal. Zephrys has gotten some shiny new toys from recent expansions, perhaps most notably the Demon Hunter card Chaos Nova and the mega-AoE Priest spell Shadow Word: Ruin.

Kazakus: Not as reliable as Zephrys since his effect is much more RNG-dependent but still a fantastic card. The combination of effects you get off Kazakus is utterly unique in Hearthstone and can still win games you otherwise couldn't. Still a powerful card well worth running.

Reno Jackson: The man, the myth, the legend. He gives the entire archetype his name and his uniquely powerful healing is still very much appreciated in a reactive deck such as this one.

Reno the Relicologist: His battlecry is fantastic for addressing diverse board states, especially while ignoring effects like Counterspell or Loatheb that might jam up spell-based removal. Reno can mop up a board AND remains as a 4/6 to continue fighting for board. And unlike cards like Volcanic Potion or Twilight Flamecaller that see their value drop dramatically once bigger things start hitting the board (Thing from Below, Loatheb, Fungalmancer buffs, etc) Reno's deadeye aim on minions-only means as long as there is 10 health or less on board, he can kill them no matter how the stats are distributed. 

Inkmaster Solia: I still love this lady, even if no one else does. Beyond the obvious Turn 7 Solia+Pocket Galaxy play, she helps bypass Loatheb, makes 10-mana Kazakus potions playable 3 turns earlier or play a Kazakus potion for 7 mana and still have 3 left over for a Dirty Rat, Banker, Zola, Secret, Doomsayer, Frost Lich Jaina hero power, et cetera. She also becomes nuts if you discount her to 1 with Pocket Galaxy.

Dragonqueen Alexstrasza: Weirdly enough this is probably my least favorite card in this deck. A lot of the time she's too expensive to play and the dragons produced are too random to be reliable. On the flip side, her effect is unique and has so much potential upside that I can't justify cutting her. This becomes especially monstrous when discounted by Pocket Galaxy since lots of Dragons have battlecry effects, making it easy to get mega-value off of Brann/Zola/Barista.

Mad Scientist: Still good for the same reasons since Naxxramas released. A decent enough body that draws a card and puts it into play for free is just a really good deal. 

Flame Ward: Can be a real lifesaver against a lot of aggro/tempo boards. Being able to hit 3 damage is great and the fact that it can be set up in advance or put into play for free by Mad Scientist or discovered by Arcane Keysmith is great for keeping pace with a faster adversary. Much in the same way a Doomsayer forces a fast opponent to reevaluate their plays, Flame Ward forces suboptimal choices and gives you breathing room to find more solutions. 

Ice Block: The enabler of mega comebacks, messes with OTK combos, too good not to include.

Arcane Keysmith: Secrets are one of the only ways to interact with your opponent’s turns and having more of them is fantastic. Has proven to be especially clutch in the face of revived Razakus Priest decks, providing redundancy in secrets by finding extra Ice Blocks or messing up a combo turn with Potion of Polymorph and/or Explosive Runes.

Polymorph: Boar: Helps prevent resurrection effects from N'zoth and Gul'dan, otherwise playing double-duty as a pseudo-Silence to neutralize things like a Hench-Clan Thug or Magnetic-buffed Mech, and the occasional Albatross. Also has added versatility as a source of 4 Charge damage to make sneaky lethals happen.

Polymorph: Denies resurrections, silences buffs or deathrattles, provides ping targets for Frost Lich Jaina. Still a very powerful card.

Cloud Prince: Originally just added to this deck on a whim, this card has been very good to me. It fills a lot of niches that were previously empty. First and most obvious is that it acts as removal for midgame threats, helping kill Emperor Thaurissan and Thing from Below outright while also dealing potentially crippling damage to Flamewreathed Faceless or any of the myriad 8/8s in the game (Sea Giant, Mountain Giant, The Lich King). Second is that it puts something into the deck that Reno Mage typically lacks, which is a way to deal damage to face. I've surprised opponents who thought they were safe at 13 health or less, only to play Brann+Cloud Prince and hero power to burn them to 0. Third is the fantastic fact this is an elemental so the battlecry and any subsequent attacks with the decent 4/4 body afterwards will provide more lifesteal.

Siamat: I think I was one of the first people to use this card in Wild and he's really proven himself over hundreds of games. Depending on which buffs you choose for Siamat, he can deal 6 to a single target, deal 6 to two separate targets, deal 12 to a single target, and often stick around to attack again the following turn. Top it all off with the fact that he's an elemental for some added late-game sustain and Siamat is a great fit for this deck.

Book of Specters: With the density of high-impact minions in our deck and the fact we run a minimal number of spells, the discard drawback is significantly mitigated. In a deck where so many powerful cards can turn the game around, this big draw is very much appreciated. 

Dirty Rat: Very much a tech card that gets swapped in and out. Currently used as a valuable tool against Jade Druids, Togg Druid, lategame Razakus Priest, mid-to-lategame Cubelock and a few other decks. 

Doomsayer: Handy against Secret Mage since it tests for about half the Mage secrets in the game at once (Mirror Entity, Potion of Polymorph, Explosive Runes), useful for stalling out rising stars in Even Shaman and Demon Hunter and also has utility against Darkest Hour Warlock by stalling for a crucial turn.

Gluttonous Ooze: Pirate Warrior is still a thing, Cubelock is still a thing, Secret Mage is still a thing. Having some weapon destruction can be very helpful and including it in our deck naturally means less pressure to draw Zephrys for a solution. 

Stargazer Luna: Replacing my old fishy friend Coldlight Oracle. As powerful as Oracle was, the rising power of Even Shaman and Demon Hunter made the drawback outweigh the benefit. Immense synergy with Pocket Galaxy (appropriately enough) and enables backbreaking plays 

Escaped Manasaber: Provides a solid body, the stealth makes it hard for opponent's to remove and the added mana smooths out your curve very nicely. Even something as simple as playing this on Turn 4 and skipping to 6 mana on Turn 5 to play Reno the Relicologist or Reno Jackson early can be very handy indeed.

Loatheb: Helps lock out combo turns from Quest Mage and Razakus Priest and Togg Druid, slows down development from things like Jade Druid and Darkest Hour Warlock and Quest Mage. Reduce his cost with Galaxy and duplicate him with Barista and Zola to drag the effect out for multiplte turns.

Skulking Geist: There's been a noteworthy resurgence of Jade Druid/Togg Druid following the addition of Kael'thas. Geist finds value in destroying Jade Idol, Floop's Gloop, Biology Project. There is also a fringe benefit of using it to destroy the multitude of 1-mana spells that included or generated by various forms of Quest Mage.

Baleful Banker: This deck tends to draw a lot of cards and having something to offset fatigue in long games or to go infinite in rare ultra-value matchups can be quite handy. Otherwise functions like an extra Zola to help generate even more copies or important cards.

Brann Bronzebeard: He’s made 1 mana 5/6 and 2 mana 4/5 crabs, drawn or discovered extra secrets, brewed massive potions, healed me for 10 while destroying enemy weapons, yanked out combo pieces, infinitely staved off fatigue. Fantastic card for our deck and pairs well with the bevy of battlecries we have.

Zola the Gorgon: Sort of like Brann in that it helps squeeze extra value out of the numerous powerful Battlecries we have.

Leyline Manipulator: Between Zola, Barista, Malacrass, Zephrys, and Kazakus potions there's plenty of generated cards that benefit from getting such a huge cost reduction. Combo this with Brann and watch the madness ensue. 

Barista Lynchen: Most of the deck consists of battlecry minions, so it's not too difficult to get good value. Basically if your opponent leaves any 1 to 2 battlecry minions alive, Barista will pay for herself once you play her, especially if you get some help from Pocket Galaxy.

Luna's Pocket Galaxy: This deck is very minion heavy so it's not difficult to get some serious value out of setting things to 1-mana. Even if you hit something relatively small like Brann or Kazakus, you'd be surprised by the sheer amount of things you can squeeze into a single turn with Galaxy smoothing things out. Plus there's the hilarity of the OTK combo to look forward to! (see below)

Hex Lord Malacrass: Alongside Dragonqueen Alexstrasza, this is one of the big value targets for Pocket Galaxy to land on, generating more resources to push you over the top. Since you always want to look for your high-impact cards in your opening hand anyway, it is not to difficult to get a good hand to duplicate with Malacrass. That said, he is another very high-cost, high variance card and might warrant replacing in future. 

Frost Lich Jaina: Presents the threat of a ceaseless tide of Water Elementals, turns Cloud Prince and Siamat into massive heals, looks AMAZING with the golden animations.