Undersea Kingdom: Chapter 3 – Arena of Death

Undersea Kingdom (1936) is a Republic Pictures 12 chapter film serial released in response to Universal's Flash Gordon
Plot: Unga Khan (wearing Black Robes), wishes to conquer Atlantis and then destroy the upper world with earthquakes generated by his Disintegrator. Sharad the current ruler (wearing White Robes) is defending Atlantis against the usurper. Professor Norton leads an expedition, including Lt. Crash Corrigan and reporter Diana Compton, in his rocket submarine to the suspected location of Atlantis. Upon finding the lost continent, they join into the fray knowing that if they fail and Unga Khan wins, the world above is doomed.