Prelude is an expansion to Terraforming Mars, and can be combined with any other Terraforming Mars expansion or variant.

As the mega corporations are getting ready to start the terraforming process, you now have the chance to make those early choices that will come to define your corporation and set the course for the future history of Mars - this is the prelude to your greatest endeavors!

In Terraforming Mars: Prelude, you choose from Prelude cards that jumpstart the terraforming process or boost your corporation's engine. There are also 5 new corporations and 7 project cards that thematically fit the early stages of terraforming a new planet.

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Prelude 2: New twists await your terraforming efforts. 

Terraforming Mars: Prelude 2, the sixth expansion for Terraforming Mars, focuses on cross-expansion effects, prelude cards with ongoing effects and actions, and more project cards for your tableau...not to mention five new corporations.

Most of the cards are specifically connected to other expansions of Terraforming Mars (Venus, Colonies, Turmoil), but the 5 Corporations and 15 of the Prelude cards are playable without any of these other expansions.