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The next Hearthstone expansion was confirmed by Blizzard just over a week ago, and it goes by the name of The Witchwood.

There'll be the usual 135 new cards to tuck into when the new content goes live in April, a handful of new keywords to experiment with, and a new single-player adventure to explore in the form of Monster Hunt.

Yesterday evening we had the chance to catch up with Hearthstone's senior game designer Peter Whalen. We talked about everything that's been revealed of The Witchwood so far, as well as reinvigorating some of last year's less successful new archetypes, and how the team hopes to avoid another Corridor Creeper situation in the future.

Odd / Even additions to the UI MB: I had a look in the game just before this interview, and thinking about the odd and even synergy coming with The Witchwood, there's no functionality in the UI right now to look for odd or even cards. Is that coming? PW: It is. When you add one of the odd or even cards - like Baku the Mooneater or Genn Greymane - to your deck it'll give you a prompt that says "Do you want to change your collection filter to just show odd or even cards?", depending on what's been put in. If you then hit yes it will only show odd or even cards. If you want to view them without adding one of those cards, you type in something like cost:odd or cost:even - something like that. MB: Is there any other UI functionality that's going to be added? PW: When the game starts you'll be able to see Genn or Baku come up and they'll say something to you, and there's an effect that plays that says your hero power is being upgraded or the cost is being reduced to one. Both players will see that and so it's like the Prince Malchezaar moment so you can see what's going on.

Hagatha the ??? MB: Looking at the hero card that's coming. It's quite unusual to see an "old new" thing from a previous expansion return, and I was curious to see why it's for the Shaman. Is it because of the class's current poor status in the meta right now? PW: Not at all. It's really about the story. This is The Witchwood expansion so this is all about the spooky forest outside the town of Gilneas. We've got these werewolves, the Worgen in WOW that are fighting against the creatures of the forest, led by Hagatha the Witch of the Woods. PW: It was really important to us that we capture Hagatha as the central character of the expansion in her mechanics. How can we make this one character super, super special? The answer was: let's make her a hero card. Lets make her a different card type to every other card in this expansion so we can highlight that she is the most important character. MB: Why the Shaman? PW: Story-wise she is a Shaman and the Witch of the Woods. There were a couple of different classes that we thought she could maybe be, but it made sense that she was this twisted, evil shaman doing horrible things, transforming the spirits into bad, evil things. MB: On the subject of Hagatha there's a lot of interest in her because the reveal was so mysterious. Can you give us any kind of tease or clue about her mechanics that we don't already know from that video? PW: We'll show enough in the next couple of weeks... MB: No teasers until then? PW: That's all I got, sorry!

New keywords MB: Moving onto the keywords, if we look at Charge, which has been so problematic for Hearthstone in the past - Grim Patron Warrior and so on - did you ever consider just changing Charge to what Rush is now, and if not why now and not back then? PW: We talked about that a lot. Whether it was better to change Charge, introduce a new keyword, or introduce a new keyword and also change all of the Charge cards to be Rush. PW: The biggest thing that we talked about was you know what Leeroy Jenkins does, you know what Stonetusk Boar does. You know what all these old cards do and changing that is pretty disorientating. It would also mean that these old cards would become much, much weaker. Leeroy would get much worse, so we decided not to do that yet. PW: I think it's something we still have on the table for the future, but at least for right now we're really excited about Rush and seeing what kind of cards we can make with it, because you can't attack your opponent's face with a Rush minion. You still have a lot of opportunities on the design side to put in powerful things. PW: Look at Militia Commander. We can't make that card if it has Charge. 4 Mana 2 / 5 Charge, Battlecry: Gain 3 Attack this turn? It's just insane. With Rush though it's a card that we can make, and it's pretty cool and exciting to play with. MB: It's an opportunity to do more with Charge without risking another really broken scenario where the meta's overwhelmed with face decks? PW: Charge as a mechanic is really fun. It's really great to be able to play a card and do something with it immediately. It's why Battlecries are really fun. If we can take Charge and get rid of the parts that are problematic? PW: The thing that's not fun about Charge is having your opponent do 20 damage to you on a turn from an empty board. That's pretty miserable. We want to find ways to make cards that you get the fun on your side of having Charge minions, but not have the "un-fun" of dying from 30 health or whatever. MB: Talking about keywords, take "Cannot be targeted by spells and hero powers". Why hasn't that been made a keyword by now, because it's quite a mouthful and it seems like the kind of thing that's crying out for a keyword simplification. PW: That's a challenging one to keyword because it's not obvious exactly what it does. When you write it out, it's totally obvious. If you keyword it - I've heard Elusive as one of the words that people toss around on the internet - there's a question of what is allowed to target it? PW: It can be targeted by attacks, it can be targeted by Battlecries, but it can't be targeted by spells or hero powers? Remembering exactly what that list is is trickier if it's keyworded, but much easier if it's written out explicitly. MB: It's not like Poisonous where you can grasp what's going to happen pretty intuitively? PW: Yeah Poisonous is a good example where you can just kind of guess.

Reinvigorating old archetypes with new cards MB: Looking at some of the archetypes from 2017, there were loads of different ones that bubbled up - some stayed in the meta for a long time, some didn't. Are there any archetypes from last year's three expansions that weren't as competitive as you wanted them to be, and that you are now targeting to empower in 2018 before they rotate out of Standard in 2019? PW: I'm not sure there's anything in particular where we're saying "This is an archetype that was weak, let's make it amazing right now". It's more we're going to put a lot of tools out there, especially for those archetypes that didn't see as much play. We're also going to put out tools to let new stuff come up. The odd and even stuff is a great example of new mechanics and new archetypes. PW: Another one is Taunt Warrior. This is a good example of a deck that saw a bunch of play back in Un'Goro and hasn't really seen a lot of play in the last six months - and more than that. We've got cards like Phantom Militia with the new Echo keyword, which means you can play it as many times in a turn as you want as long as you have the Mana. PW: If you're playing the Warrior Quest deck you can get three different Quest triggers with it. Conveniently, both the Warrior Quest and Phantom Militia are both odd, so if you tossed Baku in your deck... MB: There's one deck I loved that never really seemed to cut through to the upper tiers of the meta which was the Big Spell Mage concept... PW: I think Big Spell Mage has been quite good, we've seen a bunch of play for it at high Legend and also in competitive play. Are Mages going to get more big spells this year? I think there's a pretty good chance we'll release more spells for Mage that cost more than five. Whether we're going to make more cards that trigger off of "You have to have only big spells in your deck"? We'll see.

New additions to the Hall of Fame MB: Looking at the Hall of Fame now that Ice Block's moving in there. Ice Lance was sent there to try and get rid of Freeze Mage and it still took a long time for that deck to fall out of favour. Now Ice Block is going to the Hall of Fame to try and do the same for Secret Mage. What is it about the Mage that makes it so stubbornly resistant to this kind of archetype change? PW: [LAUGHS] PW: I think it's less that these are targeted at Freeze Mage*, it's more that Ice Block in particular is a card that's been around for a long time. It's been around since beta and the start of the game. It's a really cool and interesting and different thing, but at the same time it's worn out its welcome. PW: People are tired of having to kill a Mage twice - or with Discover cards and other random generation, three or four times - before they actually die. It's more we want to get rid of those play experiences rather than say "OK, we're definitely going to target Freeze Mage, or Secret Mage, or Control Mage decks. (* We believe Peter is actually referring to Secret Mage in this context.) MB: Are there any specific archetypes that you'd like to see not be so dominant in the meta going forwards? PW: In general we like seeing new stuff. Having the metagame change, having the metagame evolve over time is awesome and I think that's one of the opportunities we have with the set rotation. At the start of the new year we're going to have a lot of cards that will move into Wild. We're going to add in cards with The Witchwood. This is the time of greatest change, you're going to see a huge amount of shifts in the metagame.

Why it takes so long to nerf cards MB: Looking at the nerfs that tend to come every expansion, they tend to happen quite late in the meta. Are the team looking to move faster in the future when these problems come up, rather than having three months of broken meta and things being exciting again. PW: For Kobolds and Catacombs the metagame was quite good out of the gate. There were a lot of really fun things out of the gate and a lot of fun things people were doing. I don't think it's fair to categorise that as a broken metagame. MB: That was perhaps unfairly phrased, but if I look at cards like Corridor Creeper they were in every deck they could be forced into. There were a couple of months of that really - I remember writing about it over Christmas - and then we had the late February patch come in. That's quite a long time to be seeing those same cards, so I don't think it's that unfair to position it that way. PW: So Corridor Creeepr was a powerful card but the metagame was quite diverse. The metagame, how you count it, the number of top tier decks, the most played decks, there's a bunch of different ways you can look at those metrics. PW: But the metagame was pretty diverse and also was quite a bit of fun. That said I'm glad that we changed Corridor Creeper and some of the other things that we changed, so that we could open things up again towards the end of the expansion, and create another diverse and interesting and different metagame. PW: It's definitely one of the things we're always talking about. What is the right time to nerf cards? What's the right time to make changes, because there's always the danger you change cards and you end up with a metagame that's less fun than the one you just left. PW: There's certainly risks involved every time you do it. Every time you nerf cards it makes people have to change decks. It makes people's decks less powerful, and the things they loved and the things they enjoyed. If you're a player who really loves Tempo Rogue and we nerf Bonemare and Corridor Creeper, what does that do to your play experience? PW: On the other hand we have to balance that against, OK you're losing to Raza Priest for a long time. What is my play experience as someone who keeps losing to those decks, is my play experience better if we change them? We have to be careful and we have to make sure we make the right changes, but its always something that's not obvious what exactly is the right kind of change. PW: On the back-end we're looking for more technical solutions so we can change cards without requiring players to download as much content, without making as drastic a change to the game. Having a client patch, there's always a bunch of things for people to download and it creates inconvenience for a lot of players. On the back-end that's something we're looking at to smooth out that process. MB: When you look at experiences with cards like Corridor Creeper, how does that inform your development of new expansions? Do you have a mental Corridor Creeper test when designing cards now, and thinking about how it could be broken? PW: Sure, every time we release a card that's more powerful than we were hoping for - or makes a combination that's more powerful than we want - that's something we think about for the future. OK this card is like Raza, this card is like Corridor Creeper, this is like Bonemare. Maybe that means we should re-think it a little bit more.