Discover in Boomsday – What Can You Expect to Find in This Standard Format?

The Discover mechanic has been an awesome addition to Hearthstone, and we’ve sang praises to it before. It is so uniquely digital and yet skill-intensive: play a card, get to choose one of three different cards from a specific pool of cards. Some pools are small and you can predict very well what you can find, while some pools are large and the variance is bigger.

In this article, I’m digging bit deeper into the figures for The Boomsday Project Standard format. You are probably aware of the basic ground rules: you can only Discover cards that are Neutral or from your own class, and class cards are more likely to be offered. However, when we know the specific card pools, we can do better than that. What can we really expect to discover in Boomsday? Let’s find out!

Arcane Dynamo

Arcane Dynamo is a new Neutral minion from The Boomsday Project that can Discover a spell that costs five or more mana. Aside from the basic issue of why would you want to put the card in your deck instead of just putting in the spell you want, we can take a look at how likely you are to find the cards you need with it.

  • Druid has eight spells that cost five or more, so the probability to discover a specific one is 37.5%.
  • Hunter has five spells that cost five or more, so the probability to discover a specific one is 60% – and this includes Flark's Boom-Zooka.
  • Mage has eight spells that cost five or more, so the probability to discover a specific one is 37.5%.
  • Paladin has ten spells that cost five or more, so the probability to discover a specific one is 30%.
  • Priest has 12 spells that cost five or more, so the probability to discover a specific one is 25%.
  • Rogue has six spells that cost five or more, so the probability to discover a specific one is 50%.
  • Shaman has five spells that cost five or more, so the probability to discover a specific one is 60%.
  • Warlock has five spells that cost five or more, so the probability to discover a specific one is 60%.
  • Warrior has seven spells that cost five or more, so the probability to discover a specific one is 42.9%.

There are major differences between classes. Whereas Priest and Paladin cannot easily find a specific card, Hunter could grab some extra copies of their Legendary spell more than half of the time.

Arcane Keysmith

Arcane Keysmith has seen quite a lot of play in multiple Mage archetypes. It has been used in slow Control Mage decks and also in Tempo Mage and Murloc Mage. Discovering powerful Secrets on-demand is a useful ability.

Mage does not receive new Secrets in Boomsday, so there will still be eight Mage Secrets in Standard format:

The probability to find a specific one is 37.5%.

Blazing Invocation

Blazing Invocation has not found its place in the meta. While spending one mana to Discover a minion is not that high of a price to pay, the pool of Battlecry minions is huge: 164 Neutral minions and 19 Shaman class minions. It’s not easy to find what you need from a pool that large, and indeed, your chance to find a specific Shaman class minion is only 5% – and the chance to find a specific Neutral minion is only 1%. That’s nothing to write home about.

Chittering Tunneler

Chittering Tunneler has seen occasional play, but it has not exactly been a strong card. As new expansions are added, the card pool grows and it is now at 31 Warlock spells in Standard. The probability to find a specific spell is therefore down to 10%.

Dark Possession

Dark Possession has seen occasional play in more control-oriented Warlock decks after its debut in The Witchwood. The current Standard card pool includes 20 Warlock class Demons and five Neutral Demons, so the probability to find a specific class Demon is 14% and the probability to find a specific Neutral Demon is 4%.

With Void Analyst bringing in additional Demon synergies again, it might not be too bad, although most decks that are interested in Demon synergies would rather deal damage to opponents than to their own face.


Dendrologist is one of the many new Treant synergy cards in The Boomsday Project. It remains to be seen whether the archetype is viable, but we can take a look at Dendrologist individually regardless. There are 38 Druid spells that you can Discover with Dendrologist, so the probability to find a specific one is only 8%.

However, things don’t look quite as bleak if you group up the cards a bit. For example, there are nine cards that can deal damage to the opponent (including cards that give your Hero attack), so you can find one of those 57% of the time. Likewise, eight cards can give you tokens, so you can find some more minions 52% of the time. Or, if you’re looking to buff up your Treant board, there are eight cards that buff at least one minion for a 52% chance there as well. Dendrologist may not always give you the best possible card, but it can often provide you with a card of a specific type.

Free from Amber

Free From Amber is a Spiteful Priest classic that has seen its play rate decrease as Spiteful Priest went away from the meta. In Boomsday Standard format, there are 31 Neutral minions you can Discover with Free from Amber and then there is Obsidian Statue – still the lone Priest class card. You still have a reasonable 31.32% chance to Discover Obsidian Statue, while the chance to Discover a specific Neutral minion is 8.67%.

The new additions to the pool from Boomsday, Mecha'thun and Bull Dozer, have decent stats, so they do not significantly weaken Free From Amber. It’s still a solid card, if it can find the right deck.


Hydrologist has long been one of the most reliable Discover cards. Getting to choose one card from the small pool of Paladin Secrets is unlikely to go wrong.

Boomsday adds Autodefense Matrix to the mix and brings the number of Secrets in the pool to six:

Therefore, you have an exactly 50% chance to Discover any specific Secret.

Myra Rotspring

Myra Rotspring is the new Rogue Legendary minion. It allows you to Discover a Deathrattle minion and also gives Myra a copy of its Deathrattle.

The math part for this Discover is the easy part. There are 5 Rogue Deathrattle minions and 41 Neutral Deathrattle minions in Boomsday Standard format. Therefore, the probability to Discover a specific Rogue Deathrattle is 18.96% and the probability to Discover a specific Neutral Deathrattle is 5%.

However, evaluating Myra is more complicated than that. It requires a subjective evaluation of how many of those cards are any good.

Rogue cards are the most important ones:

All of these have their uses, but none of them is strikingly powerful – there are no Mechanical Whelps or Cairne Bloodhoofs here (although you could hit those as a Neutral option).

Out of all the available cards, 15 summon something when they die – that’s a 73% chance to find such a Deathrattle! However, may of these are mere 1/1s and may not be enough to make a difference. Furthermore, another 13 cards give you more resources, either generated or drawn, that’s a 69% chance to get that. Once again, though, many of these are not very powerful resources.

Myra can give you many types of things. Whether she can provide enough tempo or enough value is more difficult to judge.

Omega Assembly

Omega Assembly promises tons of value. The one-mana Discover spells have generally been lackluster, but at 10 mana crystals you can grab three Mechs in one go. Maybe go all Boom before that and you can even grab some Rush Mechs? Doesn’t sound bad at all.

There are four Warrior class Mechs in Standard, all of them from The Boomsday Project:

There are also 34 Neutral Mechs in Standard right now – 26 of them from The Boomsday Project! So, the probability to Discover a specific Warrior Mech is 23% whereas the probability to Discover a specific Neutral Mech is 6%.

How good are these Mechs? The Warrior class Mechs are all situational. They are good in some cases, but there are no unconditional superstars among them.

We can examine the overall Mech pool also through some keywords:

  • Seven of the Mechs are Magnetic – 50% to Discover one of them.
  • Four of the Mechs have Rush – 23% to Discover one of them.
  • Five of the Mechs have Taunt – 28% to Discover one of them.

These are not quite Deathstalker Rexxar figures, so you cannot reliably expect to get anything specific.

These same figures also apply to the Delivery Drone phase of the Dr. Boom, Mad Genius Hero power.

Primalfin Lookout

Primalfin Lookout does not see much play even in Murloc decks as they tend to be more tempo than value-oriented, but it can dig for some good cards if needed.

Only two classes have class-specific Murloc right now: Paladin has Hydrologist and Primalfin Champion whereas Shaman has Brrrloc and Ghost Light Angler. For those classes, the probability to find a specific class Murloc is 55% and the probability to find a specific Neutral Murloc (out of 11) is 17%. For all other classes, the probability to find a specific Neutral Murloc is 27%.

If you have a Murloc deck that is looking for some resource generation, Primalfin Lookout is not bad at all.

Primordial Glyph

Primordial Glyph has seen a lot of play in faster Mage decks. More face damage, surprise board control, you name it, Primordial Glyph can deliver it. Sometimes, anyway.

There are currently 39 Mage spells that can be Discovered in the Standard format. Therefore, the probability to discover a specific one is slightly below 8%.

However, the true power of Primordial Glyph becomes more apparent when we group up the spells a little:

  • There are eight Secrets, so the probability to find one is 51%.
  • There are six spells than can go face, so the probability to find one is 40%.
  • There are seven spells that deal area-of-effect damage, so the probability to find one is 46%.
  • There are six spells that can freeze a minion, so the probability to find one is 40%.

While you may not find a specific spell very easily, you can find a specific type of effect almost half of the time.

Servant of Kalimos

Servant of Kalimos has not been able to find a stable slot in any deck. Elemental Shaman has been too predictable to succeed and Elemental Mage has not quite risen to prominence either. After Ragnaros, Lightlord rotated out of Standard format, Elemental Paladin has not quite had the tools either. Boomsday only brings two new Mage Elementals and four new Shaman Elementals to the game, so an Elemental uprising is not to be expected.

That said, it is interesting to examine what Servant of Kalimos can do in those two classes in particular.

There are currently 18 Shaman class Elementals and 10 Mage class Elementals in Standard format alongside 20 Neutral Elementals. Therefore, the probability for Shaman to discover a specific class Elemental is 13% and the chance to Discover a specific Neutral Elemental is 3%. For Mage, these figures are 20% for a specific class Elemental and 5% for a specific Neutral Elemental. If you have a dream involving Pyros and Bonfire Elemental, you are likely going to be disappointed.

Stonehill Defender

Stonehill Defender has seen a lot of play in various control decks and in almost all archetypes of Paladin. The ability to Discover some additional Sunkeeper Tarims has turned out to be pretty good.

In the current Standard card pool, there are 38 Neutral Taunt minions. Paladin has four class Taunts now that Boomsday added Annoy-o-Module. Mage and Warrior remain unchanged: no class Taunts for Mage and five class Taunts for Warrior. Overall, Boomsday added five Neutral Taunt minions and only one class-specific Taunt minion, the Paladin one.

Therefore, Paladin has a 21.26% chance to find that Sunkeeper Tarim and a 5.66% chance to find a specific Neutral Taunt minion. Mage has a 7.89% chance to find a specific Neutral Taunt minion (like The Lich King). Warrior has a 19.92% chance to find a specific class Taunt, such as Cornered Sentry, and a 5.27% chance to find a specific Neutral Taunt minion.

The Runespear

The Runespear has never exactly been awesome. Boomsday added another five Shaman spells, bringing the total to 34. Therefore, the probability to find a specific spell is only 9%. Because the targets are random, many of the spells can also backfire. Alas, Discovery is a powerful mechanic to mitigate negative effects. Even though there are 11 spells that can backfire, you are offered only such spells a mere 2.8% of the time.

The new Shaman spells in Boomsday are:

Notably, none of these spells are targeted, so they improve the consistency of The Runespear somewhat.

Secret Plan

Secret Plan is the new Hunter Secret Discovery spell.

There are currently eight Hunter Secrets in Standard format:

Therefore, the probability to find a specific Hunter Secret is 37.5%. Secret Plan shows some promise, because it has a decent level of consistency and the Hunter Secrets are not bad overall.

The other Discover cards

There are also some Discover cards that do not pick from a pool of cards available to you in the current format, but from a different subset. These often pick from the deck of one of the players, such as Shadow VisionsStitched Tracker, and Cloning Device. Their odds change all the time as the game goes on and the remaining deck changes. Therefore, it is not useful to go into much detail on them.

Furthermore, some Discover cards pick from huge card pools, such as Hallucination and Explore Un'Goro. Here we get to probabilities in the region of 0.5% to 2% to find a specific card, and it is difficult to be very analytic about the possible outcomes. They are cards that you just play and see what you are offered.

What Can You Expect From Discover in Boomsday meta?

Not a whole lot has changed compared to The Witchwood meta. There are not that many new Secrets, Taunts, or Elementals, for example, so the numbers do not drastically change. Cards that Discover Secrets continue to be consistent and class-specific spell Discoveries also continue to be fairly reliable – with Dendrologist added to the mix for Druid spells.

Paladins can still expect Stonehill Defender to find good cards and Free From Amber is as strong as ever.

The new additions Myra Rotspring and Omega Assembly are interesting and exhibit a mediocre level of consistency, so they could well find spots in the right decks. Arcane Dynamo varies depending on the class from fairly unreliable to somewhat consistent – would a Hunter use it to make it more likely to get to play the Legendary spell, for example?

Anyway, these are the numbers. It is good to be aware of the general probabilities both for deck-building and for making in-game decisions, but there is always a level of interpretation involved as well. How many of Myra’s potential Deathrattles do you consider to be good? How many of the Hunter Secrets are worth Discovering? Pure numbers have a hard time answering such questions, and the answers will change with the meta as well. Going in with realistic expectations on how often you will discover particular cards helps you make decisions, but ultimately you need to make the call in the end.

What about you? What do you expect from Discover in Boomsday? Which Discover cards do you intend to play with? Let me know in the comments!

Old Guardian

Ville "Old Guardian" Kilkku is a writer and video creator focused on analytic, educational Hearthstone, and building innovative Standard format decks.

Check out Old Guardian on Twitter or on their Website!


  1. GlosuuLang
    August 5, 2018 at 10:44 am

    Why would you run a Discover card instead of the card itself? Good question, but the answer can be as obvious as: I don’t have the card or I can’t include it in my deck. Infamous example being Sunkeeper Tarim in Odd Paladin. I know that if I don’t open the Hunter legendary spell, I will include Arcane Dynamo in my Big Beast Hunter deck, just for the lolz. In any case, we all agree that Discover is a great mechanic!

  2. C0l0rs
    August 5, 2018 at 4:35 am

    first of all thumbs upf for even coming up with this topic. i mean i ll jump in the cold water and claim that you re the only person who s done a list on this topic on the whole internet. the only thing that i m missing/would change is the section about the runespear, for this weapon not only the chance of getting a specific spell matters, the keyproblem of it is it s “uncontrollability” and the fact that most shamanspells are quite cheap making this a terrible valuecard, so i would have loved to read alittle more about WHAT spells were addet to the pool cause let’s be honest i had to go to all boomsdaycards cause i couldn’t remember most shamanspells. turns out ALL the new spells are non-targetted, so they’re allready all controleable and the effects seem to be quite interesting (voltaic burst aside) for a controleshamantype. so all in all, yes, the runespear got way better with the new expansion, propably still not viable, but who knows, maybe it’s worth a try to get another potential eureka in your malyshaman for 0 mana that turn opening up for a HUUUUGE burstcombo.

    • Old Guardian - Author
      August 5, 2018 at 8:59 am

      You’re right, a list of new Shaman spells for Runespear would be convenient. I added it to the article. I do not have high expectations for The Runespear in general, but as the pool becomes better for it, perhaps it can improve to a playable status after all.

  3. JadeBuddha
    August 4, 2018 at 5:25 pm

    Very useful article! One small suggestion: consider including a summary table of the %s after the analysis text.

  4. Monkey
    August 4, 2018 at 11:28 am

    Good, informative article. More of these please!

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