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Kyurem-Black was banned from Monotype Sunday Morning.
However, this change has yet to be implemented on PS, which caused two Monotype games this week to be played with it. Out of fairness and after consulting the Tournaments Directors, we decided to allow Kyurem-B for all the Monotype matches this week, making the ban only effective for the playoffs.
Once the ban will be implemented on Showdown, you will have to play the Monotype games by challenging your opponent in the Ubers format to bypass all banlists considerations in case any player wants to use the beast. Sorry for the inconvenience
edit: apparently you can now set custom rules for challenge battles using the command "/challenge username, gen8monotype@@@+Kyurem-Black", so this works as well. The custom rules are displayed upon challenge.