Black Clover S01E116 - The Ultimate Natural Enemy

"When the owner of the four-leaf grimoire is filled with despair, the five-leaf clover grimoire will be born." Patry is filled with despair after learning he had been manipulated by the devil all this time and turns into a dark elf. He then starts attacking Yuno and Asta, fueled by nothing but hatred and malice. Somehow, becoming a dark elf had made Patry even stronger, which gives Yuno and Asta an even harder time fighting him. Then Captain Nozel appears before them. Nozel happens to have the best magical attribute to fight against light magic, mercury magic.