Tommy J generously allowed us to host his decks and guides using (mostly) Basic cards to take down One Night in Karazhan Heroic bosses. Be sure to check out his YouTube Channel.
This boss is probably the most frustrating in all of the Hearthstone expansions so far. I worked on it for literally days – somewhere around 12-18 hours trying different decks and strategies to see what worked best. While I did get within 1 turn of winning multiple times with a fairly cheap deck (280 dust), it’s definitely not something that’s doable on an even semi-regular basis. As such I went with what I would consider to be the next cheapest deck; the one listed above, where if you have zero of the three cards required it would cost 1800 dust to craft. I’ll discuss that cheaper deck below, as if this more expensive one is out of reach for you and you’re desperate to get it done cheaply, something similar to this will likely be your best bet.
So with this deck the strategy is fairly simple – hold off as best you can against Nazra until at least turn 8, play Kel'Thuzad, buff him with Ancestral Spirit, and transition into Malchezaar. Since when Twisting Nether lands the Kel’Thuzad from Ancestral Spirit will actually revive the original, it will be smooth sailing from then on if you have a few Taunts.
Mulligan
Maelstrom Portal, Acidic Swamp Ooze, Rockbiter Weapon, or any other early plays you can get.
Cards to Add
Firstly, swap out the Frostwolf Grunt for Pompous Thespian; it’s literally just a better card and is free (thanks /u/BabiesDrivingGoKarts ). Anything stronger than what’s already in the deck would increase your chances, particularly with Nazra. Be careful adding cards with Overload, since they can set you behind.
Cards to Remove
Murloc Tidehunter, Razorfen Hunter and Frostwolf Grunt are the cards I would remove if I had a better alternative. Bloodlust is also a potential candidate, but it can help either pushing Nazra down, or finishing off Malchezaar. If you aren’t a fan of the random legendaries you can also remove Prince Malchezaar, but I feel in a deck like this they do more good than harm.