That Time I Got Reincarnated as a Slime (2018)

S2E23 Returning from the Brink

Clayman and his minions are hopelessly outmatched by Rimuru and his team. In a desperate move, Clayman commands Milim to unleash Stampede and eliminate everyone, but Milim surprises him by revealing she was never under his control. Her deception was meant to unveil Clayman's schemes and reveal the true puppet master. Moreover, Carrion is still alive and unscathed. As he faces imminent defeat, Clayman taps into the souls of his slain victims to fuel his transformation. This sets the stage for the climactic showdown between Rimuru and Clayman.