Dark Hero is a Weiß Schwarz card from Disgaea DG/EN-S03-E161. Compare listings from Singapore Weiß Schwarz sellers on CardJio, then jio them on WhatsApp.
You may put the top card of your clock into your waiting room. Choose one of your characters, and that character gets the following ability until end of turn. "【AUTO】 When this card is put into your waiting room from the stage, you may return this card to its previous stage position as 【REST】."