Global Ruin
Sorcery
Oracle Text
Each player chooses from the lands they control a land of each basic land type, then sacrifices the rest.Rulings (2)
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Wizards of the CoastIf a land counts as multiple basic land types, you can choose it for either or for both of those land types.
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Wizards of the CoastYou sacrifice all lands other than the chosen ones. Since you can only choose lands with basic land types, any non-basic lands that don’t have a basic land type (even if they have some other land type, as in the case of Cloudpost) are necessarily going to be sacrificed.