In the beginning of the film, Thor is not a hero; he is an arrogant, warmongering prince. He violates a treaty, almost starts a war with the Frost Giants of Jotunheim, and is stripped of his hammer, Mjolnir, and his powers by his father, Odin (Anthony Hopkins). This is classic "Hero’s Journey" storytelling, executed with precision.
Thor is banished from Asgard for his arrogance thor.2011
Meanwhile, Loki discovers his true lineage as a Frost Giant’s son, betrayed and adopted. His subsequent betrayal—sending the Destroyer to Earth and attempting to wipe out Jotunheim—sets the stage for the entire MCU’s most complex villain arc. In the beginning of the film, Thor is