Thor 3 overview: more of a quest narrative structure than a superhero plot structure. In this, Thor is actually a reluctant hero, content with staying out of the business of Asgard and living the simple life on Earth. Through his journey, he learns that he cannot abandon his responsibilities (its not enough to just be a good man when the fate of the nine realms rests on you, unfair though it may seem).
PROLOGUE: Surtur in Muspelheim DOOM! hammering [this should be revisited periodically between key scenes throughout act 1 and 2 to show how Surturs army is growing]. Unlike the previous Thor movie prologues, I wouldnt have Odin narrating this. Partly to underscore the fact that Odin isnt around, and partly to highlight the primal, stark power of Surtur.
ACT I: Thor on Earth with Jane. He is content with his life there. Think of how Thor was acting at the end of Thor1, when he was humble and enjoying the simple life, like making eggs for his friends, etc. Sif arrives suddenly and says Odin is running Asgard into ground w/ strange advisors (Amora & Skurge). She says that Thor is needed but she suggests he return not by the front door because Odin might not welcome him back. Sif stays to watch over Jane at Thors request, with tension between the two. Thor returns to Asgard not via the Bifrost, but through Nornheim (via Karnillas magic).
In Nornheim, Thor meets Balder, the long-time ambassador from Asgard, and Karnilla, sorceress and leader of Nornheim. They fill Thor in on how things have gone downhill. Many of Asgards faithful have fled or (those who did not succumb to the strength of Skurge or the seduction of Amora, like the W3) been banished. They have sought refuge on other worlds, like in Nornheim (in the MCU, Id make Nornheim the home of the Valkyrior). Karnilla also warns the she feels a great evil growing with sights set on Asgard, and urges that if Thor loves what Odin/Asgard once stood for, he must get through to Odin (or says for the good of all the universe, Odin must stand against this evil, etc).
Thor sneaks into Asgard through the troll caverns. He runs afoul of Ulik, and defeats him after a brief but destructive battle. By the time the fight with Ulik ends, Thor has caught the attention of Odin and is retrieved by the Einherjar, who are waiting for him when the dust settles. They are led by Skurge; Thor and Skurge briefly skirmish, but Thor stops fighting when he sees that the Einherjar seem not to be themselves. During their battle, Skurge boasts that he is the new champion of Asgard, and demonstrates that his axe is as powerful as Mjolnir (so he believes). After he surrenders, Thor is brought back to Asgard.
ACT II: Asgard is dirty, no longer the Golden Realm. The citizens seem downtrodden, & somehow hypnotized or in a trance. Thor is brought before Odin, who bids that all but Skurge and Amora leave. Thor pleads that Odin snap out of it to prepare for the coming evil, but Odin reveals himself to be Loki. Thor is ready to kill Loki, until Loki reveals that Odin is alive, but hidden away (in Niffleheim, a dark and dingy word of ancient citiesthe same place the Aether was hidden in TDW; also, for the MCU, combined with Hel
?). Loki acknowledges that he knows an evil is coming. It is Surtur, coming to light his Twilight Sword with the Eternal Flame (seen in Odins vault in Thor1), which will destroy the Nine Realms. Loki has been using Amora to enslave an army for Asgard, but he knows that it wont be enough and concedes that he needs Odin. He says that only Thor can retrieve him. As insurance, Loki reveals that he has Sif and Jane as prisoners (Heimdall, enthralled by Amora, pulled them there using the Bifrost; there was no fight; magic is not a fair or honorable way to fight in a world of warriors, but thats how Loki operates).
Thor sets out for Niffleheim via the Bifrost, but must navigate the dead world upon his arrival. He is immediately surrounded by the denizens of Niffleheim, and must battle through the endless hordes until they are stopped by their master (Hela? Or perhaps some other Thor foe here
), who makes a bargain to return Odin, on the condition that The Son of Odin take his place upon his death. Thor agrees. Odin is weak beyond belief. They return to Asgard.
Loki restrains Thor and takes Odin, revealing his true plan was to siphon the remaining Odinforce into himself using Amoras help. At this time, Karnilla, Balder, and the Warriors 3 arrive with the Valkyrior (via Pegasusi) and attack to reclaim Asgard. This was their plan all along, arranged by Thor before he left. Karnilla and Balder are an equal match for Amora and Skurge, while Thor fights Loki, the W3 find and release Jane and Sif from captivity, and the Valkyrior fight the Einherjar forces. Jane and Sif team up with Karnilla on Amora, who is defeated (maybe Jane does something science-y, or maybe Sif sneaks up while shes distracted and runs her through). With Amore dead or incapacitated, Skurge, the Einherjar, and everyone else in Asgard are released from their enthrallment, just as Surturs forces arrive. Loki runs into hiding.
ACT III: Surturs forces storm into Asgard over the rainbow bridge. Heimdall puts up a valiant fight but is gravely injured, the first casualty against Surtur himself: a towering being of fire taller than Asgards great hall; a true force of nature, unlike anything the Asgardians (or audience) have ever seen before. Thor, Sif, Balder, and the W3, with Skurge behind them, reach the end of the rainbow bridge; Thor flies out to Heimdalls observatory and grabs him, then circles around Surtur to truly take in his scope before returning to the others. When he lands with the W3, Skurge says Ill hold the bridge, and the others are forced to trust him as they fall back to the great hall. Skurge fights singlehandedly and eventually makes the ultimate sacrifice as Surturs forces overwhelm him, but he buys the others enough time to escape.
Meanwhile, Jane and Karnilla have Odin in a healing room and have helped him regain some power. He is still weak, but he says he must face Surtur alone. Thor arrives and says Odin will not be alone. Jane reasons that if Amora was able to siphon Odins power, there must be a way to do the opposite, and combine the powers of Odin and Thor. Karnilla says she can do that, and it might work. Just then, Loki comes out of hiding and says That wont be enough. Ill stand with you today.
Thor, Odin, and Loki move to the highest tower of the great hall, with Karnilla by their side. Sif guards Jane, but Jane takes up a sword herself; they have a mutual respect now. Below, fire demons fight with Valkyrior in the sky as the Warriors 3 lead battalions of Einherjar on the ground. Karnilla begins an incantation, as Surtur continues to lay waste to Asgard left and right. Surtur has approached the great hall. He looms above the tower upon which our heroes stand and raises the Twilight Sword above his head with both hands. Karnilla completes her incantation, and a massive Godblast emanates from Odin, Thor, and Loki. It is blinding.
When we can see again, Surtur staggers backwards, dropping the now broken Twilight Sword, his own flames diminished. Thor takes flight and delivers blow after blow with Mjolnir in hand, mercilessly striking with lightning bolts from space, unleashing all his might, until Surtur is pushed back beyond Heimdalls destroyed observatory and falls into the chasm of space. Thor returns to the tower. Odin has collapsed. He dies.
EPILOGUE: Asgard is in ruins. Thor takes the throne in a solemn ceremony that is a sad echo of the coronation scene that opened the first film. Thor banishes Loki (to Niffleheim, repaying Hela with a son of Odin), and returns Jane to Midgard in a move of self-sacrifice. Whether he wants it or not, it is his responsibility to lead/rebuild Asgard. He vows to return to earth if it is in jeopardy, but he cannot abandon his responsibilities for love or personal bliss again. The character journey Thor began in the first film has reached a logical conclusion.