The Demon Sword and Crona's weapon partner. Unlike most weapons, Ragnarok is inhuman in appearance, appearing as a black creature with white eyes, gloves, and a large "X" covering his face. He was melted into Crona's blood by Medusa, giving him a symbiotic relationship with Crona. He protrudes from Crona's body whenever he appears, most commonly from Crona's back. He devours souls under Medusa's orders in order to turn Crona into a kishin. He constantly bullies Crona, which reinforces Crona's shy and naive personality. Ragnarok is initially barely the size of Crona's head, but grows larger in size as he devours more souls, eventually gaining the power to become a winged dragon-like creature. Ragnarok provides Crona control over the black blood, increasing Crona's strength, hardening to reduce damage, and creating projectile weapons once it leaves Crona's body. While performing a "Scream Resonance" with Crona, Ragnarok unleashes a high-pitched scream from a mouth on the blade of his sword form, causing it to vibrate and cause additional damage.