Hearthstone

Originally subtitled Heroes of Warcraft, Hearthstone builds upon the existing lore of the Warcraft series by using the same elements, characters, and relics. It was first released for Microsoft Windows and macOS in March 2014, with ports for iOS and Android releasing later that year. The game features cross-platform play, allowing players on any supported device to compete with one another, restricted only by geographical region account limits.

The game is a turn-based card game between two opponents, using constructed decks of 30 cards along with a selected hero with a unique power. Players use their limited mana crystals to play abilities or summon minions to attack the opponent, with the goal of destroying the opponent's hero. Winning matches and completing quests earn in-game gold, rewards in the form of new cards, and other in-game prizes. Players can then buy packs of new cards through gold or microtransactions to customize and improve their decks. The game features several modes of play, including casual and ranked matches, drafted arena battles, and single-player adventures. New content for the game involves the addition of new card sets and gameplay, taking the form of either expansion packs or adventures that reward the player with collectible cards upon completion.

In contrast to other games developed by Blizzard, Hearthstone was an experimental game developed by a smaller team based on the appreciation of collectible card games at the company. The game was designed to avoid pitfalls of other digital collectible card games by eliminating any possible plays from an opponent during a player's turn and by replicating the feel of a physical card game within the game's user interface. Many of the concepts as well as art assets were based on those previously published in the physical World of Warcraft Trading Card Game.

The game has been favorably reviewed by critics and has been a success for Blizzard, earning nearly US$40 million per month as of August 2017. As of November 2018, Blizzard has reported more than 100 million Hearthstone players. The game has become popular as an esport, with cash prize tournaments hosted by Blizzard and other organizers.

Set within the Warcraft universe, Hearthstone is a digital-only, turn-based collectible card game which pits two opponents against each other. Players select a hero from one of ten classes. All classes have unique cards and abilities, known as hero powers, which help define class archetypes. Each player uses a deck of cards from their collection with the end goal being to reduce the opponent's health to zero.

There are four different types of cards: minions, spells, weapons, and hero cards. Quests are a specific type of spell only found in three expansions. These cards are ordered by rarity, with Legendary cards being the rarest, followed by Epic, Rare, Common, and Basic. Blizzard releases expansions of additional cards every four months to increase the variety in the metagame. The game uses a freemium model of revenue, meaning players can play for free or pay to acquire additional card packs or content.

Unlike other card games such as Magic: The Gathering, Hearthstone was designed to speed up play by eliminating any manual reactions from the opposing player during a player's turn, and setting a timer for each player's turn. During a turn, players play cards from their hand using "mana", a budget each player must abide by which increases by one each turn with a maximum of ten, and with cards having various mana costs. This invokes strategy as the player must plan ahead, taking into account what cards can and cannot be played. Minions and spells are unique.

Minions will be placed directly onto the board after being played and may carry special effects like Charge or Deathrattle, allowing the minion to attack instantly or making the minion do something special upon death, respectively. Spells have distinctive effects and affect the board in various ways.

Cards can be obtained through opening card packs or by crafting them with arcane dust.

The normal gameplay mode is one-on-one matches between a player and a randomly selected human opponent. Within this, the Standard game mode uses prepared decks limited to cards from the Core set alongside the expansions from the last two years. A separate Wild game mode allows all past and present cards to be used subject to deck construction rules. Both Standard and Wild game modes are divided into Casual and Ranked modes. Players can climb the tiered ranking system in Ranked, while Casual allows for a more relaxed play-style. At the end of each month the Ranked season ends, rewarding players with in-game items depending on their performance.

Other more specialized multiplayer modes include the following:

Arena has the player draft a deck of thirty cards from choices of three cards over several rounds. Players continue to use this deck against other Arena decks until they win or loses a number of matches, after which the deck is retired and players gain in-game rewards based on their record.

Tavern Brawls are challenges that change weekly and may impose unusual deck-building guidelines.

Battlegrounds, introduced in November 2019, is based on the auto battler genre, allowing eight players to compete in each match by recruiting minions over several rounds. Players are paired off randomly in each round, with combat between minions played out automatically, with the goal of having minions remaining to damage the opponent's hero, and ultimately be the last hero standing. The top 4 hero's place and earn a win and increase rating points while the bottom 4 earn a loss and decrease rating points.

Duels, introduced in October 2020, is a multiplayer version of Hearthstone's singleplayer "Dungeon Run" game mode. Players start with a 15-card deck they assemble themselves, and (like Arena) battle other players until they win or lose a number of matches, after which the deck is retired and players gain in-game rewards based on their record. After each match, the player chooses between three 'buckets' of three cards each, or a treasure card to add to their deck. Unlike Arena, there is a casual mode that requires no entry fee.

Classic mode uses a mirror of the player's library of all cards that were in the game as of the June 2014 release of the game, reverting any updates or changes to these cards in the interim, effectively representing the game's start at the time of its release.

Mercenaries, introduced in October 2021, is focused on a party-based combat system with roguelike mechanics. A player creates a party from six minions from a central Minion Village and uses that party to complete various quests, both as player-versus-environment and player-versus-player. Battles in this model use a color-coded system similar to rock paper scissors where minions of one color are strong against another color but weak to the third color. Players use this system and minion abilities to try to win battles. With loot gained from combat success, players can use facilities in the Minion Village to improve the attributes and abilities of individual minions or recruit new minions.

In addition to these multiplayer modes, there are solo adventures. These adventures offer alternative ways to play and are designed specifically to challenge the player.

The following table lists the card set releases by their name, type, North American date of release (with the release in other regions typically within a day afterward), the date of the expansion's removal from the Standard format, and the distribution of cards within that set.

Initially, Blizzard introduced an alternating series of Expansions and Adventures, with roughly three new sets released each year. Expansions are new card sets, containing between 100 and 200 new cards, that become available to buy or win, as well as introducing new mechanics to the gameplay. Adventures feature smaller number of cards, around 30, which can only be earned by completing multiple tiers of story-based challenges and boss fights in single-player mode.

In 2017, Blizzard changed their approach, and focused on Expansions and mini-sets for cards, with adventures providing non-card rewards.

Later, Blizzard moved away from Adventures as they found that because Adventures gated the set's cards until the challenges were completed, these cards did not readily enter the meta-game, and when they did, they would be used more by expert players who could easily complete the Adventures' challenges compared to amateur players.] Blizzard recognized that players do enjoy the single-player narrative events and have worked in quests and missions around the new card sets for those players. Examples of these quests and missions include facing the bosses of Icecrown Citadel with Knights of the Frozen Throne's release, and the new dungeon run feature which appeared in the Kobolds & Catacombs expansion.

Blizzard has adopted a "Year" moniker to identify when expansions rotate and retire from Standard format. At the commencement of the first year, "Year of the Kraken" (from April 2016 to April 2017), Blizzard retired the Curse of Naxxramas and Goblins vs Gnomes sets. At the commencement of the second year, "Year of the Mammoth" (from April 2017 to April 2018), Blizzard retired the Blackrock Mountain, The Grand Tournament and League of Explorers sets. At the commencement of the third year, "Year of the Raven" (April 2018 to early 2019), Blizzard retired the Whispers of the Old Gods, One Night in Karazhan and Mean Streets of Gadgetzan sets. Initially, after such time as the adventures and expansions were retired, these sets were no longer available for purchase. However, due to player demand in July 2017, players were again able to purchase these retired sets and all future sets that are retired from Standard by using real money on Blizzard's online store. In the "Year of the Mammoth", Standard moved some Classic cards to the "Hall of Fame" set that is not playable in Standard but the cards still can be obtained and are available to play in Wild format. In the "Year of the Raven", three additional Classic cards were moved to the "Hall of Fame" set.

In 2021, Blizzard introduced an annually rotating Core set that can be used in Standard and Wild modes. The first iteration of the set consists of 235 cards: 31 new ones and 204 selected from various non-Standard sets. The Core set is free to use for all players ranked at least level 10 with all classes. With the introduction of the Core set, the Basic, Classic, and Hall of Fame sets were grouped into a Legacy set confined to the Wild mode. Alongside the Core set, Classic mode was introduced where only the original 2014 versions of cards from the old Classic set can be used.