Episode 11 of "Nanatsu no Maken ga Shihai Suru (Reign of the Seven Spellblades)" is a high-stakes episode focusing on intense battles and revelations. The episode begins with a duel between Oliver Horn and Joseph Albright. Oliver manages to counter Joseph's spell technique, but Joseph retaliates with a swarm of stinger bees. Joseph offers to erase the memories of the fight if everyone surrenders, but the group refuses.

Meanwhile, Chela reveals her half-elf heritage, which allows her to perform a double summoning—a feat usually too exhausting for human mages. She and Marco unleash a powerful spell, giving Nanao the opportunity to repel the bees with her spell, "Elletardus." The duel ends with Oliver defeating Joseph, who for the first time tastes and appreciates the flavor of defeat.

The episode also delves into the backstories of several characters. Joseph Albright shares a painful memory from his childhood, revealing the immense pressure he faces as a member of the Albright family. Chela recounts her complicated relationship with her half-sister Stacey, who is also revealed to be a daughter of Theodore McFarlane. Stacey is determined to outshine Chela to gain their father's recognition.

Just as the episode seems to be winding down, a new crisis erupts. Magical beasts suddenly appear and abduct several students, including Fay and Pete. The episode ends with the shocking news that Ophelia Salvadori, a mage with succubus blood, has been consumed by her own spell.