RNG Series: Un’Goro Edition

EDIT: Thanks to @Old_GuardianHS for reminding me adapt is 3/10 not 3/9. Post fixed.

When I first started this blog in the last quarter of 2015, I wrote a bunch of posts where I tried to quantify RNG in the game, the RNG Series. I guess doing the math became too much work for me, as it appears I have not written one of these in 2016 or 2017. Upon the release of all the Journey to Un’Goro cards yesterday, I felt that this expansion had quite a bit of reduction in randomness. Let’s go in and see look at all the random effect cards, and try to quantify some probabilities.

Hearthstone Screenshot 04-26-16 20.02.29.png
Un’Goro RNG ain’t your Old Gods’ RNG


  • Single Adapt (12 cards) = 3/10 = 30%
  • Double Adapt (2 cards) = 1 – (7/10)^2 = 51%
  • Galvadon = 1 – (7/10)^5 = 83%

Single Adapts are easy to calculate, just 3 out of 10 outcomes. For multiple Adapts, the events are independent, meaning each roll will be 3/10. So when Galvadon screws you over by not getting Stealth, that was a 17% chance. It will happen.


  • Hydrologist = 3/5 = 60%
  • Primalfin Lookout = [3/18, 3/14] = [16.7%, 21.4%]
  • Chittering Tunneler = 3/25 = 12%
  • Tortollan Primalist = [3/32, 3/25] = [9.4%, 12%]
  • Free from Amber = 3/30 = 10%
  • Primordial Glyph = 3/32 = 9.4%
  • Servant of Kalimos = 3/36 = 8.3%
  • Stonehill Defender = [3/56, 3/49] = [5.4%, 6.1%]
  • Curious Glimmerroot = 3/59 = 5.1% + Your Brain
  • Hallucination = 3/59 = 5.1%
  • Explore Un’Goro = 3/366 = 0.8%

Discover cards all have a numerator of 3, since you are selecting 1 of 3 picks. The denominator will vary quite a range. Hydrologist has a fairly low RNG, as there will only be 5 Paladin secrets in Standard. While Curious Glimmerroot has an inherent 5.1% of a card, you will likely know what class card is in the opponent’s deck. Also since Discover picks from the pool of Class + Neutral, some cards will vary like Primalfin Lookout for Murlocs, Tortollan Primalist for Spells and Stonehill Defender for Taunts. Explore Un’Goro draws from a pool of Warrior + Neutral cards, giving a 0.8% chance for each card.

Random Card Advantage + Molten Blade

  • Crystalline Oracle = [1/26, 1/1] = [3.8%, 100%]
  • Megafin = 1/19 = 5.3%
  • Molten Blade = 1/23 = 4.3%
  • Elise the Trailblazer = 5/135 = 3.7%
  • Lyra the Sunshard = 1/31 = 3.2%
  • Shimmering Tempest = 1/32 = 3.1%
  • Stampede / Jeweled Macaw = 1/76 = 1.3%

Crystalline Oracle will vary depending on how many cards are left in the deck, so highly variable, but limited in Constructed with repeated cards. Megafin will give a 5.3% chance for each Murloc, and that probability will increase depending on how many cards you get to draw. Stampede and Jeweled Macaw had the probability for a desired Beast plummet after the heavy insertion of Beasts in the new set.



  • Tortollan Forager = Turn 2 – 5 attack minions
  • Arcanologist = Turn 2 – Secret
  • Tol’vir Warden = Turn 5 – 2 1-cost minions
  • Mimic Pod = Turn 3 – Anything

Draw cards always start off with a limited denominator of how many cards are left in a deck. Turn 1 players start with 26 cards, while the Coin player starts with 25 cards in deck. Then you subtract what turn a card can be played on inherent card draw. So, the Tol’vir Warden for example, will likely be drawing cards from the smallest deck pool, on average. Mimic Pod is the most variable of these cards, as there is no limiter on what is drawn, like Thistle Tea. Getting 5-attack guys and Secrets are likely more discriminating than 1-cost minions, but these are all random outcomes of limited probability, given the parameters of 30 card decks.



  • Volatile Elemental = [1/7, 1/1] = [14.3%, 100%]
  • Sulfuras = [1/8, 1/1] = [12.5%, 100%]
  • Volcano
    • Chance of getting hit with no minions = 99.9%
    • Chance of not getting hit with 14 minions on board = 38%

Back in GvG, random damage appeared to be the main mechanic. Surprisingly, there are only 3 cards like this in the expansion. Volatile Elemental will range from 1/1 to 1/7, so that can obviously be modified. The Ragnaros hero power from Sulfuras will include the hero, so that bumps an extra character. Volcano, obviously is highly variable, depending on it’s own randomness and how much stuff is on the board. With an empty board, the chance of a hero dodging 15 shots is 0.0031%, so nary impossible. On a full board of 14 minions and 2 heroes, the chance of something not getting hit once is 38%. Of course, there are more complicated calculations depending on how much health everything has, as a minion with 1 health dying off will increase the odds of everyone else getting hit. Too complicated.



  • Giant Anaconda = [1/10, 1/1] = [10%, 100%]
  • Cruel Dinomancer = varies

Again, we’re not in GvG, when Piloted Shredder dropped off anything. Giant Anaconda at the least has a 10% chance, and this is the highly unlikely scenario of having a hand of 10 5-attack guys. Cruel Dinomancer can be controlled by how much discard you are running. If Clutchmother Zavas was thrown away a lot, she will likely be the most likely outcome of summon, as a 2/2.

The upshot

It’s safe to say that Team 5 took the feedback that bad RNG is bad for the game and competitive Hearthstone. Most of the RNG in Un’Goro is Discover and Adapt, outcomes which have a skill requirement to it. Cards with really wacky RNG outcomes likely won’t be all that good in this set. A card like Stampede is likely a card advantage engine, where you’ll just be looking to get “A Beast” rather than “OP Beasts.”

I think that state of the RNG discussion will focus on the Discover cards, since there will always be variation in a pool of 59 or so cards. Adapt is pretty safe as a mechanic, with the 30% probability floor (not to mention multiple good Adapts).

Elements of Hearthstone RNG: Shaman/Range

Thrall lives and dies by the elements, but when he calls for a totem, it could be 1 of 4 characters. That in itself makes the Shaman the most random class in Hearthstone. The Shaman also specializes in cards that a provide a range, what I call “Shaman RNG.”

Did the 4 dead guys take 5 or 6 damage? We will never know.
Did the 4 dead guys take 5 or 6 damage? We will never know.


Lightning Storm/Elemental Destruction – The Shaman board clears go 2-3 damage or 4-5 damage, only proving a slim range in damages. To maximize the damage, try to get a Wrath of Air Totem out. Weaken bigger minions that don’t immediately dies from these spells. Play around these cards by having good-sized minions. You usually play around Lightning Storm (since it is more seen) by making sure all the minions on your board have more than 2 health. Having 3 health minions would put your minions at a 50% chance of dying. Having minions that are 4 or bigger will prevent any minions from dying off. Nobody really plays around Elemental Destruction, but maybe you can get a read off your opponent in the arena, as if they are going to play a Flamestrike.

Random Attack Points

Fireguard Destroyer – This card has a unique effect that no other has at the moment. For a cost of 5, you will get something between a 4/6 minion to a 7/6 minion. That makes a 25% chance of getting a 4/6, 5/6, 6/6, or 7/6. Basically, you have a 25% chance to get something that costs less than 5, a 25% chance to get something that costs exactly 5 (Pit Fighter), and a 50% chance to get something that is worth more than 5.

Single-Target Damage

Dr. Boom – As mentioned in the previous RNG post on pings, the Dr. has two types of RNG. Each Boom Bot hits a random character for 1-4 damage. The flying bombs will range from 2-8 damage combined. The most likely chance is 5 damage (33%), followed  by 4 and 6 (25%), 3 and 7 (12.5%) and 1 and 8 (6.25%). Ah, so that’s what those War Golem buff people are all meaning.

Imp-losion – This card hits one minion for 2-4 damage. Hitting for 2 will summon 2 1/1s, which is about 3 mana’s worth. Hitting for 3 will summon 3 1/1s, which is about 3.5 mana’s worth. Hitting for 4 will summon 4 1/1s, which is about 5 mana’s worth. There is a bit of swing here in terms of mana worth, with the 4 damage outcome being a great savings. It is boosted by spellpower, so that is a great combination to have for the arena, or some weird Malygos Warlock.

Crackle – With a 3 damage range affixed to a single-target spell, Crackle is the most RNG card of all these cards. 2 + 1 is basically a cost of 3. At 3 damage, you are only getting 2 mana’s worth. At 6, you are getting a Fireball, which is a spell that costs 4. When using Crackle, it’s best to hit a minion with health that gives you at least a 50% chance of killing it. Not a good idea to use it on a 6-health minion, since that gives you only the 25% chance for removal. Of course you can get screwed by 25% chance you get a weak shot. Again, this is boosted by the spellpower totem, which would ramp the damage to 3-7. Crackle’s RNG is more evident than that of other cards, since it can also go face.


  • The only way to take advantage Shaman RNG is to have spellpower. Dr. Boom and Fireguard Destroyer are at the whole mercy of randomness.
  • There isn’t much you can do here. Which puts Crackle in the group of one of the most frustrating cards ever, or one of the most miraculous ones.

The Elements of RNG: An Introduction

If you’ve ever browsed a forum, blog, or website about gaming, there’s a good chance you have encountered the phrase “RNG.” The acronym itself stands for “random number generator” and typically refers to any random element in a game, or anything subject to probability/chance. As it stands, RNG remains a major issue for Hearthstone.

Typically, RNG is invoked as a complaint by more experienced players losing a game to lesser experienced players, and it does provide a fudge factor in reducing the gap between skill levels. The level of RNG in Hearthstone has often been used by blowhards as the prime reason why they have quit the game. At other times, the RNG in Hearthstone is said to be a good thing, or something that made the game unique. Often, an instance of extreme RNG serves as an amazing highlight reel shot.

So how much RNG is there in Hearthstone? I sought to find out.

What this is

  • I pored over every collectible card in Hearthstone released so far. I was able to bin every card containing a random element into a type of RNG. I was able to discern 14 types of RNG.
  • Some cards have so much randomness, they fall into multiple bins!
  • I try to rank the amount of randomness of each card in each bin.
  • I try to talk about how people lessen the randomness and increase their odds of success.

What this is not

  • I don’t compare Hearthstone RNG to that of other games.
  • I’m not taking a side about whether RNG is bad or good for Hearthstone. I am objectively talking about each type of RNG.

Truth about card games

  • Here’s the inconvenient truth. Every card game has RNG. As long as cards are drawn from a deck, there is an element of probability of what card you get.
  • There is a 30 card requirement in a Hearthstone deck. That means there is a 3.33% of drawing a single card. In constructed, the randomness of drawing cards is reduced by including 2 copies of a card. This means there is a 6.67% chance of drawing it.
  • Cards like Varian Wrynn and Far Sight and Call Pet aren’t really RNG. Cards that have randomness depending on card draw are just at the mercy of being in a card game.
  • The same goes for topdecking. Sure it’s luck you drew the card you needed for lethal, but it’s just the nature of randomness in a card game.

The remaining posts of the RNG series will discuss in depth each of the 14 bins I identified as a source of RNG in Hearthstone.

Stay tuned!