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In page Spelljammer:

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The Spelljammer: AD&D Adventures in Space space fantasy boxed set was released in 1989.[1] Several of TSR's other campaign worlds had their own sections in the Spelljammer Boxed Set - Realmspace for the Forgotten Realms, Krynnspace for Dragonlance, and Greyspace for Greyhawk. Along with the new sphere - Clusterspace - they were known as the "Big Three and Astromundi". Dark Sun, Ravenloft and Mystara weren't included, as the first two did not fit with the setting and the Mystara only used the D&D rules, not the AD&D rules.[citation needed]