It allows WoTC to add - in very small quantities - abilities and keywords to the client that they can test in bursts that are manageable. This lets the eventual adding of larger quantities of these cards (pioneer, modern, etc) much easier.
Anyway, thought that was pretty cool.
External link →I think it was Ben who said that all the old sets work, but they wont relese it yet because they arent as polished as the new sets.
A few cards here and there regress. For Amonkhet block, around five cards got minor problems as a result of being untested for two-ish years of development. Not too bad for machine-generated code I think! #wotc_staff
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