Following her performance of the maedjinn's requiem, Muse Nostrolo explained that the metallic djinn she had been forced to create are now susceptible to destruction, and because it was magnified by the crystal arca, it wasn't just the immediate maedjinn, it was all of them, even those still in the realm of their creation; the Aether Wroughtlands! I am not sure if the Djinn Sovereign was truly slain, but we will make sure he doesn't have an army soon enough.