Mjölnir is the hammer of Thor , the Norse God of Thunder. A replica version of it was temporarily lent to Issei Hyoudou.


Mjölnir is a giant hammer with a black outer frame with a blue structure throughout its entire design from the head to the handle. There is a Norse symbol on its middle piece. In the anime, when having its power boosted by Issei's Boosted Gear, the Mjölnir gains a glowing design expanding throughout the hammer.

Light Novel versionEdit

The original Mjölnir doesn't appear in the Light Novels, but a replica of the Mjölnir was handed to Issei to assist him in combating Loki and Fenrir. Despite being a replica, it retains the ability as the actual one, causing Issei to originally face difficulties in using the Mjölnir replica due to its sheer weight. This was overcome however when Issei used Pailingual on Akeno and accidentally gained the blessing of Chichigami allowing him to use the Mjölnir replica and defeat Loki, after striking him with the lightning produced by the replica boosted by the Boosted Gear.

The hammer itself is light as a feather and bears no weight, except for those who have any evil feelings, as the hammer can only be wielded by those with a strong and pure heart. In Volume 13, it was explained by Surtr Second that Mjölnir was forged by the Dwarves from the Ívaldi Tribe for Thor.

Anime versionEdit

The real Mjölnir is summoned by Odin to the battlefield where the young Devils, Irina and Rossweisse are battling Loki and his monsters. Like in the novels, the Mjölnir is handed to Issei who transfers the Boosted Gear's power into the hammer, striking Loki with the hammer and defeating him.


Mjolnir fully charged

Mjolnir after being charged up with the Boosted Gear

Mjölnir is a weapon that only a God can wield. The hammer is capable of releasing powerful lightning and thunder attacks capable of defeating a God. The replica of the Mjölnir lent to Issei also displayed the same abilities as the original one. The replica is capable of increasing or shrinking in size when manipulated with Demonic powers.

While not shown to have a shrinking ability, in the anime, the Mjölnir, after being boosted by the Boosted Gear, increased in size when Issei attacked Loki. It's also shown to have a sealing ability as Issei used it to trap Loki.


  • In the anime, Issei never faces any difficulties in using the Mjölnir.
  • In the anime, the Mjölnir never controls any thunder or lightning, aside from releasing lighting when sealing Loki.