Black Clover Episode 51: Proof of Rightness
Episode 51 of 170 of Black Clover, aired September 25, 2018, 25 minutes. Available with English subtitles and dub where released.
Episode summary
After Captain Yami saved the Black Bulls in the Underwater Temple, Yami and Asta return the stone to the Wizard King and report what happened when suddenly a large enemy force arrives at one of the Clover border cities near the Diamond Kingdom... a Great Enemy has appeared, but the Golden Dawn Magical Knights Squad is rushing in.