The Phyrexia: All Will Be One Update Bulletin is the place to find information about changes to the Magic Comprehensive Rules that are coming with the set's release, as well as updates to the official text of some cards. This document is written while the rules and card text changes are still going through editing, so it's possible they'll be a little different from the final changes. When the rules are finalized, you'll be able to see them on the rules page. Once the set is live, official Oracle card text for each card can be found at Gatherer.
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Comprehensive Rules Changes