Given Qyburn's hand in Cersei's administration(?), I'd assume that room was probably equipped with weapons of torture. I don't know if any of you watch Salem, but my natural assumption was that the mountain torturing Unella like the "House of Pain" for suspected witches... Really gruesome tools there.
It's kinda cringey to talk about, but it would be odd/awkward for the mountain to rape her given her legs were tied iirc, in a pretty closed position (

) And he looks like his genitalia would fall off anyway


