Diantha has just been revealed from SM6 Forbidden Light. The set will be released in Japan on March 2nd, and then in America on May 4th. Thanks goes to Bangiras for the translation.
You can only play this card if 1 of your [Y] Pokemon was Knocked Out during your opponent’s last turn.
Choose 2 cards from your discard pile and put them into your hand.
You can play only 1 Supporter card during your turn (before your attack).