Random effect

Yogg-Saron, arguably the most random card ever released

Random effects are effects which include some degree of randomness or 'RNG' (random number generation).

Random effects introduce an element of chance into Hearthstone. They can be interesting, fun, frustrating or rewarding, but their outcome is always uncertain. For a discussion of the role of randomness in games, see RNG.

Notes

• Effects which draw randomly from a pool of cards are influenced by game format, with only cards valid in the current format being eligible for selection. All other random effects are unaffected by game format or game mode.

• Random effects without specific influencing factors are "truly random" and offer balanced chances of all possible outcomes, regardless of circumstantial details such as which minions are currently on the board or which cards are currently in the player's hand. Random outcomes are also not affected by game mode, such as Tavern Brawls (unless specifically stated). However, some effects are limited by clearly relevant factors, such as Totemic Call, which will only summon a totem that is not already present, or card draw, which can only draw cards that are remaining in the player's deck.

• Random effects do not always feature the word 'random' in their description. Game Designer Ben Brode explains that the general strategy is to explicitly state 'random' for effects that take place in "visible zones" such as the battlefield or the player's hand; and not to explicitly state 'random' for effects that take in "hidden zones" such as the opposing player's hand, or either player's deck. However, Brode acknowledged that not all cards follow this convention, stating that "the word 'random' just feels better on [some] cards", while in other cases adding the word 'random' would simply complexify card text too much. Players must therefore expect that effects which affect hidden zones will be random, even if this is not specifically stated on the card. In addition, Deathrattles and triggered effects are never targetable, and so are always random, whether or not this is stated.

• When a card has "a 50% chance to attack the wrong enemy", it is unofficially known as "forgetful". More details on this type of randomness can be found on that page.

• One of the design reasons behind random effects of all kinds is to add variety, ensuring that each match feels different. This is also one reason for the limit of 2 copies per card in a deck, and the relatively small number of card draw effects in the game, preventing the cards available to players from being too consistent across games.

Random damage

Random damage comes in a few forms. Some cards, commonly Shaman cards, deal a random amount of damage (within a certain range) to one creature or each one of multiple creatures. Other cards deal an exact amount of damage to a random target, or multiple random targets.

The most complicated case is cards such as Arcane Missiles and Mad Bomber that deal a total amount of damage distributed or "split" randomly. These effects are best thought of as a set of one-damage "hits" being randomly targeted one at a time: Each point of damage is considered a separate instance of damage dealt, meaning that cards like Gurubashi Berserker and Frothing Berserker will trigger multiple times even if the points of damage came from the same spell or effect, and Divine Shields will be removed by a single point of damage, allowing the protected minion to be damaged by further "hits" from the same effect. Furthermore, damage will never be distributed to a minion that has already been brought to 0 health by previous hits from the same effect.

This concept has some exceptions. Deathrattles and other death effects from any destroyed minions occur "simultaneously" after all the damage is dealt, which means that minions summoned by Deathrattles (e.g. Damaged Golem) cannot be hit by the same effect that destroyed their "parents" (e.g. Harvest Golem), and that damage may be "wasted" on targets that would have died anyway from the Deathrattle of another dying minion (e.g. Abomination). Also, for spells which distribute damage between multiple targets, each point of Spell Damage adds one additional randomly targeted "hit", thus increasing the total damage dealt by one, rather than increasing the damage of each hit by one.

Strategy

Some RNG elements within Hearthstone can be minimised by controlling the prevailing situation. For example, Deadly Shot destroys one random enemy minion. When faced with several enemies, this can prove extremely random; however, when faced with only a single fearsome enemy its RNG element is removed, and it becomes a simple and effective removal spell.

Order of play is often important when dealing with RNG in target selection. Players may wish to first remove non-desirable targets for abilities such as Arcane Missiles and Cleave, to ensure that only the ideal targets remain available. More often though, players will generally want to use RNG abilities early in the round, in order to plan the rest of their actions around the resulting situation.

The uncertainty of RNG elements causes many players to avoid them whenever possible, preferring guaranteed effects which can be relied upon to achieve their intended goals, and RNG options are often considered to be slightly poorer than their average effect, due to the undesirability of their randomness, which also makes planning for their use much harder. However, the satisfaction of a successful roll of the dice can be very gratifying, and to some degree form a reward in itself for attempting a risky play. The seeming unfairness of being defeated by an opponent due almost entirely to luck or chance can be particularly exasperating for the loser, and particularly entertaining for the victor. Some players also choose to use cards with strong RNG elements (such as Gelbin Mekkatorque) in order to add variety, unpredictability and fun to the game.

Card draw itself is inherently a randomised process, and cards granting card draw can also be considered to provide players with random effects.

Cards

For Wild format listings, see Random effect/Wild format

This section lists Hearthstone cards and Hero Powers with random effects. Note that card draw, shuffle into deck and Discover effects are not listed here, but can be found on the linked pages.

History

In the build-up to Curse of Naxxramas, the adventure's class cards were revealed to players one by one, many of which featured Deathrattle effects, with text that did not specify that the effects were randomly targeted. This led to widespread confusion over the function of the effects. In a special forum post, Ben Brode explained that by omitting the word 'random', card text could be shortened. By establishing the rule that Deathrattles were never targetable, the developers would not have to explicitly state this on each card, which could eventually allow for the development of more "strategically deep" card effects, due to having more card space in which to describe them, potentially otherwise a limiting factor. Brode stated that "setting expectations now that triggers never allow choices allows us to make cards that otherwise would have too much text", explaining that the omission of explicit statements to this effect "lays the groundwork for shortening the text."

However, in the face of player confusion and preference for random effects to be explicitly described as such, the policy was altered, and the word 'random' added to several Naxxramas cards.

Trivia

• Gnomes are known for the unpredictability of their inventions, and many gnome cards in Hearthstone feature random effects.