Sleipnir is a NIFL special operations team formed by Major Loki Jotunheim, with most of its memebers being holders of parts of Code Lost. Its main purpose is combating Ds labeled as 'disasters', along with being one of Loki's trump cards against Charlotte B. Lord.
Sleipnir was formed at an unidentified time in the past by Loki Jotunheim as part of his experiments on Code Lost, with the intent of collective application of the scrapped factor by having it spread over multiple holders. Major Loki eventually assigned Yuu Mononobe as captain of Sleipnir and added Jeanne Hortensia into the unit at an unidentified point in time due to her remarkable eyesight, sending them across the globe to restore order in areas hit by Dragon disasters.
Shortly after Yuu was transferred to Midgard, Sleipnir was sent to retrieve Tear Lightning from the Sons of Muspell and their leader, Kili Surtr Muspelheim. Although they were successful in acquiring Tear, they were unable to capture Kili.
In Volume 4, Sleipnir was dispatched to the Principality of Erlia along with Hreidmar in order to eliminate Kili, who had sought refuge there. However, they were unsuccessful, with Jeanne defecting from the unit by the end of the operation.
In Volume 7, Sleipnir was ordered by Major Loki to take out the newly born Kraken Zwei. However, due to the intervention of Jeanne, they were unable to kill her and were subsequently injured by the enraged hybrid, putting them out of commission for the duration of the incident.
In Volume 9, in preparation for their invasion of Midgard, the members of Sleipnir received mysterious capsules from Major Loki (which, unbeknowst to them, contained the blood of Loki's father) in order to enhance the power of their fragments of Code Lost and enable them to synchronize with each other. When Midgardsormr's final defensive line was breached, Sleipnir landed on Midgard's shores, meeting up with Ariella, their last member, and headed out to exterminate Charlotte.
In Volume 10, Sleipnir, having fully synchronized with Ariella due to the blood capsules, made their way to Charlotte's chambers from underground in order to kill her, coming across Yuu and his friends in the way. Although their enhanced abilities made them a difficult opponent, they were eventually neutralized when Yuu transformed Ariella into his kind, which resulted in them losing their fragments of Code Lost and falling unconscious. They were then restrained by Yuu and Ariella and were left in the underground passage.
- Yuu Mononobe (formerly)
- Jeanne Hortensia (formerly)
- Ariella Lu (temporarily)
- Kunato Ktinos
- Otr Axe
- Regin Club
- Robin Dark
- Sigurd Gram
- Lancelot Ignite
- Nataku Yue
- In Norse Mythology, Sleipnir is an eight-legged horse fathered by Loki, which acts as Odin's steed.
- Apart from the fact that they are holders of Code Lost, the Sleipnir members' exceptional abilities also stem from the fact that they are the descendants of Atlantean soldiers, who had undergone genetic manipulation to optimize their abilities to the fullest in order to better fulfill their tasks. As such, it is implied that they exhibit relatively good compatibility with Atlantean weapons.