WARNING: The following article contains spoilers for Marvel's Black Panther, in theaters now.
If you've seen any of the trailers for Black Panther then you know Michael B. Jordan stars as T'Challa's longtime nemesis Erik Killmonger. However, Marvel Studios has a history of changing key characteristics of its main players so they fit seamlessly into its cinematic universe. Needless to say, Killmonger is subject to plenty of alterations in director Ryan Coogler's film.
In Marvel comic books, Killmonger is one of the primary foes of T'Challa, acting as a constant threat and recurring challenge to his rule of Wakanda. That aspect doesn't change from page to screen, but his motivations and experiences do.
The Killmonger of the comics has the same destination as the live-action version, but his journey is very different. His father, N'Jobu, is coerced into working for Ulysses Klaue, which results in his family's exile from Wakanda. Ending up in Harlem, New York, Killmonger (who's actually called N'Jadaka at this point) developed a hatred for both Klaue and T'Challa that festered for years.
In the film he's still the son of N'Jobu, but his family wasn't banished from Wakanda. Instead, N'Jobu is depicted as a Wakandan spy -- otherwise known as a War Dog -- who's sent to Oakland, California, in the 1990s to keep an eye on the outside world. Meeting an American woman, N'Jobu ends up having a child named Erik Stevens and promises to one day show him Wakanda. T'Chaka, N'Jobu's brother and Wakanda's king at the time, tragically kills his own brother upon finding out he had helped Klaue, so he could never fulfill that promise to his son. Killmonger pledges to fulfill his father's mission: Use Wakanda's technology and resources to help oppressed minorities flourish.
With N'Jobu portrayed as T'Chaka's brother in Black Panther, Killmonger is actually T'Challa's cousin and has royal blood. That means he has a claim to the throne, but still has to earn the mantle of Black Panther and ruler of Wakanda. In the comics, Killmonger returns to Wakanda and pretends to resolve his problems with T'Challa, and ultimately settles in a small village. As expected, he spends a lot of his time trying to ruin T'Challa's government to exact his revenge. He does actually become the king of Wakanda at one point by challenging and defeating T'Challa, but when he consumed the Heart-Shaped Herb, his body reacted poorly and he was left in a coma.