Black Panther: Wakanda Forever director Ryan Coogler explains why Namor is the sequel`s villain instead of a character like Doctor Doom. Marvel Studios launched the Black Panther franchise in 2018 to overwhelming success, as the first film broke box office records, won Oscars, and became a cultural phenomenon. It was eventually announced that Coogler was returning to make a sequel. Black Panther: Wakanda Forever eventually moved forward with a reshaped story built around Shuri (Letitia Wright) and Wakanda dealing with the loss of T`Challa after Chadwick Boseman`s passing. The other main element of the sequel is introducing Tenoch Huerta`s Namor to the MCU
Namor the Sub-Mariner is one of Marvel`s oldest characters and someone comic fans have been waiting to see on the big screen for years. Black Panther: Wakanda Forever reinvented Namor by tying him to Aztec culture, resulting in his underwater kingdom of Atlantis being renamed Talocan. The MCU debut of Namor is one of the most exciting aspects of Black Panther 2, as the marketing has positioned him as a worthy antagonist for the sequel. It is confirmed that Namor is a mutant in the film, and there is an expectation that this will be the first of many appearances by Tenoch Huerta`s underwater villain/anti-hero.
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The possibility of Namor being Black Panther: Wakanda Forever`s villain is something audiences speculated about a lot during development, but there have also been plenty of rumors about Doctor Doom. Producers have confirmed he will not appear in the sequel and that Namor was always meant to be the villain. During a new interview with Toronto Sun, Ryan Coogler was asked for his thoughts on Doom as a character, and his response included explaining why he did not want to use him as Black Panther 2`s villain and chose Namor instead. .

Reference https://screenrant.com/