Hearthpwn

This deck was built around Prismatic Lens. But unlike other similar decks, I didn't make something busted... Instead, I made something practical, with the potential of being busted!

Please upvote if you liked this deck!

The Absolute Worst Case Scenario

You could get a 7-mana & 8-mana Stonetusk Boar or Glow-Tron stuck in your hand for ages, but also a heavily discounted Kangor's Endless Army and Dinosize. And eventually, those over-costed minions could have a Val'anyr buff on them. And with a Saronite Chain Gang, it's possible to go infinite & double-buff those over-costed minions. An 8-cost 9/5 boar suddenly sounds more reasonable.

Probably the next worse scenario is when both of your Prismatic Lenses are drawn after your other spells, in which case you can use the first one to gamble getting a 1-cost reduction on a 5-cost minion, which might not be worth it. But I'll leave that up for you to decide.

Drawing Call To Arms

You could get a pre-nerfed Call to Arms, or even cheaper! The most expensive minion costs 5 mana, so the worst case scenario when Prismatic Lens draws Call to Arms is you get a 5-cost Call to Arms and a 5-cost minion (which is paying 4 mana to draw 2 cards with no change in cost).

Drawing Dinosize or Kangor's

You could get a 1-mana Dinosize, or a 1 mana Kangor's Endless Army. But you're guaranteed a cost no higher than 5 Mana, which sets up nicely for a big swing turn. And remember, Prismatic Lens could also pull the other Prismatic Lens from your deck, making it either the same cost, cheaper, or 1 mana more than usual to play. Not so bad!

WTF, Millhouse Manastorm?

It's fine! Just make sure to never play Millhouse Manastorm as long as your opponent has cards. In fact, if you keep drawing him, and he ends up being a dead card in your hand far too often, feel free to substitute him for some other 1/2-mana minion, such as Crystalsmith Kangor. BUT another thing you could do is add Piloted Reaper to the deck to potentially pull him out of your hand for free. But getting him summoned from an early Call to Arms is a pretty decent tempo swing.

OTK Finisher

You have the usual end-game OTK combo with The Four Horsemen, Zola the Gorgon, and 2x Ancient Brewmasters, with some Val'anyr, Taunt and lifesteal synergies to help out. And worst-case scenario, you will have to spend a full turn spending 2 mana on your hero power, and 8 mana on either an overpriced Zola or Brewmaster to bounce it back to hand. But no combo card should become 100% unplayable, and will likely end up having a Val'anyr buff on it to help make up for the cost.