KeyForge is a two-player game, with each player using a single deck of cards to play creatures, artifacts, actions, and upgrades. The game's aim is to gather enough Æmber (pronounced "amber") to forge three keys before the opponent does the same. Creatures can collect Æmber and fight one another, while artifacts provide unique effects. Actions are used and discarded, and upgrades are attached to creatures to improve their abilities.

Each card in KeyForge is associated with a House, with each deck containing cards from three Houses. At the beginning of each player's turn, that player declares a House – they may then only play, use, or discard cards belonging to that House. Unlike similar card games such as Magic: The Gathering and Android: Netrunner, cards do not typically require a cost to be paid such as the expenditure of mana or credits. Instead, a player may play and use as many cards on their turn as they wish, provided the cards belong to the declared House.

Each deck features a unique card back with the name of an Archon. Decks are intended not to be modified after purchase. This is intended to reduce card trading and selling so that "net decking" (the process of researching and recreating more powerful decks) is made more difficult or impossible.^[1]

New cards are released through expansion sets. Each set features 7 Houses, which vary from set to set. Houses used in previous sets may be reintroduced, or completely new Houses are added.^[2]

KeyForge was announced at Gen Con on August 1, 2018. An announcement trailer and accompanying introductory article explaining the game were published to the Fantasy Flight website, citing a launch date in the fourth quarter of 2018.^[3][4] Pre-orders for the KeyForge: Call of the Archons starter set and Archon deck were made available the same day, as well as PDF copies of the rulebook. It was also announced that KeyForge tournaments and events would be sanctioned through Fantasy Flight's Organized Play program, details of which were later announced on the Fantasy Flight Organized Play mini-site.^[5]

In the game's rulebook, Garfield wrote about the origin of the game, expressing his desire to see "sealed deck and league play" formats return to popularity. He described the contrast between KeyForge and other trading card games as:^[6]

like the difference between exploring a jungle and walking in an amusement park (...) In the amusement park experts are telling you how to play the game, the safest strategies, and what net decks to use. In the jungle you have the tools you have.

Garfield claimed that he had wanted to create KeyForge for 10 years before release, but the printing technology central to the idea was not yet available.^[7]

KeyForge was released November 15, 2018, with prerelease events taking place earlier in the month. On the same day the KeyForge Master Vault app and website were launched to help players keep track of decks.^[8]

On June 22, 2022, it was announced that Ghost Galaxy had acquired KeyForge from Fantasy Flight Games.^[9] Ghost Galaxy ran a Gamefound campaign to fund the release of the sixth KeyForge set, Winds of Exchange, in September 2022. The campaign raised over US$1 million.^[10]

In 2020, an anthology of science fantasy short stories set on the Crucible was released called Tales from the Crucible.^[11]

Also in 2020, Fantasy Flight Games released an expansion for their generic tabletop roleplaying game Genesys called Secrets of the Crucible, based on the setting created in the KeyForge game.

IGN described the game as "a bold new idea and a vastly different kind of game format", but questioned the randomization model, speculating that "people won’t be spending tons of money on single rare cards, but that may have been replaced with spending tons of money on random deck boxes in the hopes of getting lucky with a great card combination."^[7] Polygon called the game "remarkable" in a hands-on demo and suggested that it "has its work cut out for it just in establishing a marketplace presence."^[12]

Upon release, the game was well received. Tom Vasel of The Dice Tower said the decks in the initial core set "feel balanced" and praised the unique aspects of the game and the gameplay.^[13]

KeyForge won both the Fan and Academy selected Best Collectible Card Game awards at the 2019 Origins Awards.^[14][15]

• Theel, Charlie (15 December 2018). "KeyForge: The red-hot card game where every deck is unique—and unchangeable". Ars Technica.