In 2010, after faking his death at the Elysian Fields Hotel, Gabriel came to Loki and his family for help in hiding. While Sleipnir, his father and his siblings initially welcomed Gabriel, Loki blamed Gabriel for Lucifer killing Odin at the Elysian Fields Hotel. As such, Loki had Sleipnir and his siblings ambush Gabriel while he was sleeping, bind him and sell Gabriel to the Prince of Hell Asmodeus.
In 2018, Gabriel escaped Asmodeus' custody and came after Loki and his family for revenge, killing Fenrir. Narfi and Sleipnir discovered Fenrir's body with Sleipnir finding Fenrir's bottle of alcohol nearby. Sleipnir make an inappropriate crack about Fenrir's drinking habits, causing Narfi to tell him off. After tasting the blood on the ground, Narfi identified it as that of an archangel, causing the brothers to realize that Gabriel was the killer. Visibly worried, Sleipnir called Loki to warn him.
Sleipnir and Narfi quickly tracked Gabriel to the Winchester's motel room where they attacked the hunters. Sleipnir battled Dean, armed with a whip while Narfi fought Sam. Dean eventually managed to disarm Sleipnir and throw him to the ground. Moments later, Narfi was killed by Gabriel who threatened to do the same to Sleipnir. Terrified, Sleipnir fled, followed by Dean who quickly lost him.
Later, Sleipnir returned to his motel room with two bodyguards. As the nearby elevator opened with the Winchesters and Gabriel inside, Sleipnir was shocked to see them but quickly ordered his bodyguards to get the three. With a snap of his fingers, Gabriel turned out the lights and a gunfight ensued in the dark. During the fight, the Winchesters killed Sleipnir's bodyguards and Sam hit Sleipnir himself in the right shoulder with a silver bullet, sending Sleipnir to the ground. By the time Gabriel turned back on the lights, Gabriel had Sleipnir pinned down and was positioned with one of his swords against Sleipnir's chest over his heart. Terrified, Sleipnir pleaded with Gabriel who only mockingly refused before Gabriel shoved the sword through Sleipnir's heart, killing him.
Sleipnir's personality matched his young appearance. He possessed little respect for his brother Fenrir and cracked an inappropriate joke about his death, though praised him for getting a few hits in. He was also a coward, fleeing after Narfi's death and pleading for his life when faced with Gabriel about to kill him. Gabriel himself stated that "Sleipnir is a lot of things, but mainly he is a coward."
Powers and Abilities
Sleipnir was a demigod with rather weak abilities compared to other deities.
- Astral Projection - Sleipnir revealed his true face, appearing as a horses head in an astral form before he attacked Dean.
- Immortality - Sleipnir was thousands of years old and would never age or die unless killed.
- Invulnerability - As a god, Sleipnir was invulnerable to most forms of harm.
- Super Strength - Though he seemed weaker than other deities, he was still able to take on Dean during the fight in the motel room.
- Magic - Sleipnir was able to capture Gabriel using a spell.
- Archangels - At full power, Gabriel could easily kill Sleipnir. Even in a weakened state, Gabriel was more than a match for Sleipnir in a fight.
- Silver - Being shot in the right shoulder with a silver bullet by Sam Winchester sent Sleipnir to the ground in great pain and effectively defeated him.
- One of Gabriel's swords - Stabbing the sword specifically created for Sleipnir through his heart was able to kill Sleipnir.
- While Sam can only be seen shooting Sleipnir, he is seen loading his gun with silver bullets as the Winchesters and Gabriel prepared to go after Sleipnir and Loki.
- Sleipnir is third on Gabriel's death list.
- In Norse Mythology, Sleipnir is the eight-legged horse of Odin and son of Loki. This is alluded to by Sleipnir eating carrots in the episode. When Sleipnir and Narfi first arrive at the Winchesters' motel room, a holographic representation of a horse head appears around Sleipnir's head, further alluding to this.
- Sleipnir was described by Gabriel as more of a 'god-begotten monster' than an actual Norse deity (i.e. a Pagan-Monster hybrid).