Unidentified port adapter
Unidentified port adapter
It seems to be a three-pin 12V fan connector. Their site mentions it offers quieter, cooler operation thanks to smart fan and water pump controls for smooth gaming. It includes built-in thermal sensors and detects PWM/DC modes at hardware level, ensuring optimal cooling performance and minimal noise—so you get the power you need without the disturbance!
Typically these items get labeled as FAN_1 or similar. Avoiding any reference to the header in the manual seems wise.