The God of Thunder is back -- and, this time, he needs the help of his bad boy brother.

"I gave you my word I would return," the hammer-holding superhero says to Jane Foster (Natalie Portman) in the first trailer for "Thor: The Dark World," which has her traveling to Asgard this time around.

The movie, a followup to both 2011's "Thor" and "The Avengers," sees Thor (Chris Hemsworth) battling Malekith and an ancient race of Dark Elves ... who have their eyes set on conquering Earth and all the Nine Realms.

Looking at the trailer, it looks like Jane gets held captive, leaving Thor to turn to Loki (who was the main antagonist in "The Avengers") for a hand. "You must be truly desperate to come to me for help," the Johnny Weir-lookalike tells his bro.

It also seems like warrior goddess Sif (Jaimie Alexander) plays a much bigger role.

And while Scarlett Johansson's Black Widow will be assisting Captain America in the super soldier's next flick, it looks like Thor is going it alone ... without the help of any of his "Avenger" friends.

The movie opens November 8 -- are you excited?

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