Thousands of years ago, Seth slaughtered his brother Osiris to take control of the Empire of Egypt. In response Bor and Odin declared war on Seth, for his insubordination and threat to Midgard. In the battle, Bor is killed, but Seth’s arm is cut off and he is imprisoned by Odin in a dormant sleep.
In near present-day Lorelei is returned to Asgard and sentenced, by Odin’s ruling, to 600 years imprisonment, under Tyr's watch, with her collar. However, Odin rules that as her true powers of beauty, seduction, and infatuation are an Asgardian gift and birthright, and that she should not lose them entirely. And so instead of using the collar to restrict her voice completely, he places a curse on the collar so that Lorelei cannot use sorcery to enhance her powers, as she was doing; she can no longer dominate and enthrall others and control them against their will.
We then jump to Odin’s death; at the moment of his death, Seth stirs from his sleep, Odin's magic loosened.
Ultimately she quietly settles into New Asgard, without drawing attention to herself.
Growing tired of Brunnhilde’s rule as the King of New Asgard, she eventually decides to leave the community. However, in her attempt to leave she draws the attention and infatuation of Daillus the Daring, who wants to follow her and be with her. Fearing that without her sorcery his infatuation will wear off, and that at best his deadweight will only bring too much attention, she kisses him and (temporarily) turns him to stone.
Meanwhile, Akela Amador is released from jail, having paid her dues, and meets up with her lifelong friend, Samantha Parrington. Reminiscing over their childhood with things such as their old imaginary friend, Bunnyhopper, Samantha laments that they haven’t seen each other in over a decade due to Akela’s circumstances, and now Samantha has to go away on philanthropic trip to film a documentary, but Akela reminds her that Samantha was the only one that came to greet Akela after her release from jail and if that wasn’t too long then being separated for 6 more months will be fine.
Next we see Seth. He has finally fully awakened and with Odin’s magic worn off, Asgard destroyed, and New Asgard forgotten about him, he escapes from his prison. Free, he tracks down one of the remaining pieces of Odin's magic left that he can sense – the collar. Upon meeting Lorelei he realizes the nature of the collar and the magic he sensed: Lorelei was Odin’s prisoner, just as he was. He convinces Lorelei to join his cause to destroy New Asgard and reign over Midgard. He removes Lorelei’s callor, freeing her from her curse, and allowing her full access to her sorcery. The two seek out a weapon for their cause – their own Valkyrie.
Lorelei comes across Samantha while filming her documentary and uses her sorcery to transform Samantha into a Valkyrie. However, with the new Valkyrie now under his control, Seth betrays Lorelei, wiping her memories and taking away all of her powers, before leaving. Lorelei comes to not knowing who she is, and the only evidence around her is all of Samantha’s belongings (minus her phone), leading her to believe that’s who she is.
With Samantha’s disappearance, the documentary creator Dollar Bill ends up getting in touch with Akela, to ask if she knew anything about Samantha’s whereabouts, as she was one of the last people Samantha had contact with in her phone (just ahead of Trish Walker). Off the phone, Akela goes to Samantha’s house, worried, only to find the confused Lorelei there. Concerned and with little else to go on and no other contacts, Akela tries to track down Phil Coulson and S.H.I.E.L.D. to get their resources to help find Samantha and figure out who Lorelei is.
Unfortunately for Akela and Lorelei, the outdated S.H.I.E.L.D. contact info she has leads her to an abandoned safehouse. S.H.I.E.L.D. is long gone except for a few odd trinkets and a wrench sitting on a table. Picking up the wrench, she disrupts and summons Tobias Ford . Tobias has aged and mastered his abilities of teleportation and focused his emotions, having spent a nonlinear amount of time in his hell realm.
Tobias regrettably does not know how she can get a hold of S.H.I.E.L.D., however, having lived with and learned much about magic, he senses something mystic about Lorelei. He teleports the three of them to his mystic contact, whom he long ago met in another realm: Hamir. Hamir recognizes Lorelei as Asgardian, and is able to reignite her memories. Lorelei tells the others of Seth (though does not tell them the truth about her past or powers). Lorelei, Akela and Tobias are ready to set out and stop Seth/save Samantha, however before they do, Lorelei requests a stop in New Asgard.
In New Asgard, she finds Dallius and, with hersorcery returned, dominates his will and gets him to steal Aragorn, the steed of the Valkyries. The three, plus Aragorn, then confront Seth and Samantha.
A battle breaks out and Lorelei and Samantha end up fighting, one on one, wherein Lorelei finally gets close enough, to snap Samantha out of Seth’s mind control with her own will domination, fighting against Seth's. With Samantha in great pain from being torn mentally in half by the power struggle of her creators, Seth decides to accelerates his plans and uses Samantha to open the gates to the dead to take over Midgard.
Seth nearly draws the life out of Samantha’s soul, however Tobias enters the hell realm and fights off Seth’s pull on her soul. Seth has Akela connect with the broken Samantha with her love and memories of their childhood, to serve as an achor point for her soul, Akela specifically focusing on their shared adventures with Bunnyhopper. Tobias is able to return Samantha’s soul, as well as, to everyone's surprise, an incarnated version of Bunnyhopper, to Earth.
Despite their best efforts though, Seth successfully raises his army of the dead. Overwhelmed by Seth and his forces, Lorelei, Aragorn, Samantha, Akela, Tobias, and Bunnyhopper are saved by the arrival of Krista and the new Valkyrior who – despite originally coming to retrieve Aragorn in the name of Brunnhilde – help the group fight back.
In a last stand, Seth ends up possessing Lorelei’s body, marking it with the Mark of Seth that dictates that only one of them can survive. Samantha is able to see a deathglow around Lorelei confirming that she is in mortal danger, with the two souls possessing the same body, and Lorelei convinces her to kill her. Samantha stabs Lorelei in the heart, destroying Seth, but also causing Lorelei’s body to turn to energy and fade away.
Samantha is welcomed in by Krista to be a member of the Valkyrior, but she agrees to return home with Akela and her new sentient Bunnyhopper, and Tobias says goodbye, for now, to his new associates, claiming that despite being own literal hell, he feels more comfortable there than staying on Earth.
In an end stinger, Lorelei is seen at the Monte Carlo Casino, using her full powers, free from Seth’s control, but very much still alive, having faked her death to avoid being imprisoned back in New Asgard.