Now That’s Random: Unpacking The Elements Of Chance In Hearthstone

Published: Sep 29, 2015 - Last Updated: Oct 4, 2022

The eSport with the highest degree of variance is Blizzard Entertainment’s Hearthstone.

There is, of course, a significant amount of skill required to play the game at an elite level; indicating the high level of variance is not intended to decry pro players as being merely “the most lucky.”


The same professional players find themselves consistently winning tournaments and topping the charts of ranked play, and it would be nearly impossible for this to happen in a game whose outcomes weren’t highly informed by skill.

Part of the skill of playing Hearthstone is having the ability to manage its numerous chance-driven, random outcomes.

The following will be a description for various kinds of chance-based mechanics, or those aspects of the game which are programmed to provide outcomes using random number generation.

In other words, this will examine the instances when two theoretical players who perform the exact same actions can receive different results because of the game’s programming.

Luck factors unrelated to individual card effects

Although much of Hearthstone’s random nature can be attributed to its wide array of quirky card mechanics, there are some key chance-driven instances unrelated to individual cards:

The coin toss

The coin toss is the first occurrence in a game of Hearthstone. It happens instantly, before any cards are drawn.

The “toss” replicates a real one, with a 50% chance to favor either player. The winner of the toss goes first and starts the first turn with four cards (three from drafting, one drawn at the start of the first turn).

The “loser” goes second, and starts his or her turn with six cards (four drafted, one drawn at the start of their first turn, and the coin). The coin offers a couple of opportunities for its owner:

  1. It enables one additional mana point to be used on the turn it’s played.
  2. It counts as a spell (relevant for cards which are buffed by playing spells).

There is a good amount of flexibility offered by the presence of an additional mana point, and it can be the difference between a mediocre turn and a great turn.

With a card such as Archmage Antonidas, for example, well-planned use of the coin can provide players another Fireball. While the developers claim that going first has a slight edge based on their statistics, the statement does not indicate anything about the value of the coin for certain types of decks.

Summoning an important minion a full turn earlier than normal (or more, as a druid) could be extremely important in securing a victory for certain types of decks. Overall, the difference feels much more important than just a standard coin toss, and it’s possible that it gives an edge to certain decks.

At this time, however, there’s not enough information to know its importance for individual decks; for now, it’s just a coin toss.

Card Draft and Mulligan

After the coin toss, players are shown a randomized selection of cards which they have the option of either keeping as is, or replacing (players choose which cards to keep and which to replace, as opposed to being forced to replace them all or not).

The main reason for replacing a card in the initial draw is that its mana cost is too high to be played in the early game. The number of mana crystals each player has access to increases by only one per turn without the influence of spells such as Wild Growth; for this reason, players obviously want to draw cards with mana costs that they can afford early on.

When playing against aggressive decks of many low mana cards (the purpose being to overrun the opponent before giving them a chance to play high cost cards), the need to draw cards that can actually be played, to enable survival into the late game stage, is extreme.

More moderate decks will run cards which form a more balanced mana curve, so their few low cost cards must be available to weather the storm. It’s possible that players can draw cards which are unplayable until as late as six or seven turns into a game.

When replacing cards, it is impossible to redraw them. There are a maximum of two copies allowed of any given card in a deck (only one copy of legendary cards), and it is possible to discard something only to draw its copy, if there are two of them.

It’s possible therefore to discard a hand of three or four unplayable to then draw even higher cost cards, or copies of the cards you just threw away. Likewise, it’s possible to draw the perfect set of cards for the early game.

One thing players keep in mind are the odds of drawing a needed card, which go up as the number of cards in the deck decreases each turn.

Card draw

Just like in poker, Hearthstone is a game in which success can be achieved based on the “luck of the draw.” Sometimes, a person will just pull the perfect card at the perfect time.

Players will occasionally find themselves in positions where one particular card will enable them to win the game on the very turn they draw it. This mechanic is obviously based almost entirely on chance (with some influence from the initial card draw/mulligan phase).

Good or bad card draw can result in an upset; the class which is expected to lose a match may draw the perfect new card every turn throughout a match.

The chance of pulling any card is obviously increased as the game goes on, and many decks are built with these odds in mind. Some decks are built with cards whose purpose is to prolong the game, and others which enable players to draw additional cards.

Sometimes, however, people simply beat the odds, or are themselves beaten by them. That this is a possibility for either player in a match is (in most cases) something of an equalizer, but it can make wagers on a player that much more worrying to make.

Obviously this is a factor which greatly affects variance, perhaps more than any other aspect of the game, but that’s true of many other card-based games as well.

The skill pros require is the ability to place themselves in a position to succeed regardless of the card that comes out, whether that means surviving in the case of the wrong card, or taking advantage in the case of the right one.

Opponent class and deck

The difference between ladder (constructed) play and tournament style Hearthstone is that “ladder” always involves matches between complete strangers. Players in ladder matches bring deck compositions and classes which are entirely random.

Part of winning and losing is simply based on what class and deck you’re facing, and the randomness of that is built into the very game itself.

In tournaments, however, there are certain classes and decks which are simply more common, or expected to be played; it would be impossible in today’s meta for there to be a tournament without a huge number of the competitors playing a Grim Patron warrior deck, for example (the link being just one example of a deck archetype with possible variations).

Knowing the types of decks which will probably be played allows other players to play a deck which nicely counters the Patron warrior, but there would then be other types of decks which their intended Patron counter performs poorly against.

The entire exchange is a series of preemptive mind games based on what your theoretical opponents could bring with them, and whether or not to care about it to the point of altering your own play style.

Which deck to bring is perhaps more important at the highest levels of Hearthstone than how well a person plays. Getting an edge on betting could involve simply trusting in a particular player’s ability to counter, or perhaps embrace and succeed with, whatever the meta of any given time is.

Card mechanics based on chance

There are hundreds of cards in Hearthstone, and new ones are added with each new solo adventure and card expansion. Cards represent either spells, minions, or weapons, and each one can have a very unique effect.

Some cards, like Fireball, Fiery War Axe, and Bloodfen Raptor, are relatively straightforward cards which have no particularly unusual effect. There are also cards like Stormwind Champion and Death’s Bite which have static effects, in that their effect is always the same.

Where Hearthstone gets a little crazy and unpredictable is when its cards take on mechanics which are inherently based on chance.

There are numerous forms that these kinds of cards take, but the more common chance mechanics can be classified in the following ways:

  1. Cards which spawn random minions, or random other cards.
  2. Cards which deal random amounts of damage, or damage/destroy random enemies.
  3. Cards which have effects that only activate a certain percentage of the time, or based on certain conditions being met.
  4. Cards which initiate the “Joust” mechanic.

Cards which spawn random minions, other cards

Perhaps the most random element of the game are those cards which, when played, result in the creation of a random minion or other card.

The following are just a few notable examples of cards which have this effect (ordered from least to most randomized):


When a player summons Ysera, she will give that player one of her 5 “Dream” cards at random. Those dream cards can be either a minion or one of a few various spell effects.

The difference between the minions and the spells can be important when the player is looking for one of those cards in particular, only to receive a different one.

Ysera’s mechanic is the least random on this list, with a 20% chance to give the player the card they’re looking for, but it is also the easiest to use in explaining the mechanic. Ysera and Unstable Portal are the only two cards which place the newly created card in the player’s hand; the others on this list summon the minion to the board instantly.

Webspinner, Piloted Shredder, Piloted Sky Golem

More random than Ysera are Webspinner, Piloted Shredder, and Piloted Sky Golem.

Webspinner has the chance to provide players with any kind of “Beast” card, be that a powerful card like King Krush, or a weak one like Stonetusk Boar. The game obviously changes dramatically depending on the Beast it summons, and the range of strengths for cards under the “Beast” classifier is very high.

There are only a few dozen beast cards in the game, and any qualify to be summoned (even the class-specific Druid card Malorne).

Piloted Shredder and Piloted Sky Golem each have the chance to summon a two mana and four mana cost minion, respectively. These cards are more randomized than Webspinner in that there are many kinds of both two and four mana cost minions.

Summoning a card like Amani Berserker will have a very different effect on the game than a card like Doomsayer, and there are many such scenarios in the four mana card pool as well. The minions these cards summon can definitely impact a game greatly, to the point of even preventing defeat.

The odds of this are slim because the context would have to be very particular, but it can definitely happen in a Doomsayer scenario.

Sneed’s Old Shredder, Confessor Paletress, Unstable Portal

Both Sneed’s Old Shredder and Confessor Paletress have the potential to summon a legendary minion; legendaries are the most powerful cards in the entire game.

Cards such as Deathwing, Kel’Thuzad, or Dr. Boom being summoned randomly can change the entire face of a game in seconds. There is, of course, a large list of legendary minions which do not have that kind of impact, but all of them have some interesting effect which justifies their legendary status.

There are dozens of possible legendary cards which can be summoned; getting the right one can cause the game to end.

Unstable Portal is perhaps the most random of all the summon cards in the game. It enables players to summon any random minion to their hand, regardless of quality or rarity. This card is so random that players cannot count too highly on it, because there will often be instances when weaker minions are given to them.

Its relatively cheap mana cost, and the reduction in the cost of the minion it summons, ensure that players will often average out to save mana on the cost of most minions they receive from it. It also provides the chance to get legendary cards.

Cards dealing damage randomly (by target or amount)

The following are examples of cards which, by design, will have some randomizing factor in the who they attack and/or how much damage they deal:

Knife Juggler and Ragnaros the Firelord

Both of Knife Juggler and Ragnaros the Firelord deal static amounts of damage under certain conditions to random enemies on the board; Knife Juggler deals damage when new units are spawned, and Ragnaros deals damage at the end of the player’s turn.

Each has an equal chance to deal damage to any of the enemies on the board; if there are none, both will always attack the opposing player directly. With one minion, the chance to attack the player directly becomes 50% and the chance to attack the minion is 50%, and so on.

The targets that each card attacks can have game altering consequences; Knife Juggler throwing a knife into the player, rather than an important minion, could mean that the opponent still has enough damage capability to win outright, or regain board control.

Likewise, Ragnaros has the potential to win an entire game if he hits the right target, such as in this game between players MagicAmy and Trump (would recommend not looking down at the comments if you’d like to avoid spoilers).

Mad Bomber, Arcane Missiles, Dr. Boom’s Boombots

The Mad Bomber card is unique for its occasional instances of friendly fire; when summoned, it deals three damage which is split randomly amongst any of the other characters that are on the board.

Friendly fire is not unique; there are cards such as Doomsayer and Baron Geddon which deal friendly fire, but their effects are predictable, whereas Mad Bomber is not.

Similar to Mad Bomber are Arcane Missiles and the Boombots summoned by Dr. Boom. The Arcane Missiles card deals three damage randomly split among enemies, as opposed to all characters, but it’s a spell rather than a minion.

The Boombots are the most interesting of the bunch; they can deal between one to four damage to a random enemy upon being killed. While the other cards mentioned can provide a minor annoyance, these Boombots can absolutely deal enough damage to win a game for the player who spawns them.

Dr. Boom is a very popular card right now because of the potential strength of these Boombots, who can theoretically deal eight combined damage to the enemy minions, or the opponent’s own health.

Cards which activate X% of the time

The following is a list of some of the cards with effects which activate only a certain percentage of the time, randomly:

Ogre Brute is just one of the series of Ogre cards which has a 50% chance to attack a target other than the one selected; this can have both positive and negative consequences. On the positive side, the Brute can sometimes avoid a Taunt, and attack the opposing player directly at a time when direct damage is needed to win the game.

The negatives are more common, however,with the Brute occasionally wasting its strength on smaller targets, or perhaps attacking the enemy directly when an important minion on low health needs to be removed. These kinds of swings are, again, potentially game changing.

Nat Pagle is a card which can be extremely useful if it can avoid being silenced or killed too quickly. Its value is mostly for decks which rely on heavy card draw early on, but it doesn’t see too much use in tournament decks. It can be summoned via Piloted Shredder or Unstable Portal, as has happened in this match between Trump and Cipher, but that is a rare outcome.

It’s a card worth mentioning, however, because cards rise and fall in their popularity, and the mechanic itself indicates that Blizzard could make more of this kind of card in the future.

Joust Cards

The “Joust” mechanic is a new one introduced by Blizzard with The Grand Tournament card expansion in August 2015.

A joust is initiated when a card with the “joust” ability is played: one card is then pulled from each player’s deck.

If the card pulled from the joust initiator’s deck has a higher mana cost than the card pulled from the opponent’s deck, the card which has the “joust” ability will receive some kind of a buff (listed on the card).

This mechanic is brand new, and is heavily based on chance. Of course, players who intend to rely on the mechanic will obviously put high mana cost minions in their deck, but even those decks must have a handful of low mana minions for the early game stages.

It is entirely possible for even a high mana cost control deck to be beaten by an aggressive, low mana cost minion deck in these jousts, though it seems unlikely.

The following are examples of cards which utilize this mechanic:

Each of these cards will have an impact on the current meta which is currently unforeseeable because of how recent the expansion is. It is likely, however, that those joust cards which do see play will have significant impacts on the game they’re in based almost entirely on luck.

Interesting to note is that, in the case of two cards costing the same amount of mana, the joust is considered to be a loss.


While all the chance-based mechanics could be intimidating in terms of betting on esports, it’s important to realize that much of the skill of playing Hearthstone is the ability to consider all the possible outcomes which are chance-driven, and to account for those when making decisions and building decks.

The game’s randomness is not at all a mystery to any of the people who play; they expect the unexpected.

Furthermore, not every card which instigates a randomized outcome will be popular in the meta at any given point. If a card isn’t generally included in the current meta, then its effect on the overall variance of a tournament game will be diminished compared to if it were popularly used.

Some cards simply do not see inclusion in people’s decks.

At the tournament level, players have an extremely good idea of what their opponent’s deck consists of based on what’s popular in the meta at that time. To keep up on the meta, Youtubers such as Trump and Kripparian would be a great resource.

The meta changes often, so an active amount of research is required to successfully wager on Hearthstone.

Michael Kaufman

Since: August 23, 2015

Michael Kaufman covers eSports and uses his knowledge of each game to help create betting strategies. He is based in New York.

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