Reminisce, a rune that once activated, lets the target feel the feelings and sensations the castor/user is reminiscing about.
A special something Rio had his system prepare, just to let anyone who left him to die, experience his pain atleast once before he kills them.
The guy who was screaming his lungs out, banging his head on the concrete floor, hoping to pass out and survive the torture, was currently going through how it feels when you're surrounded by hundreds of monsters in a stampede, when you couldn't move, couldn't dodge and can only hold your head and bow down as blind beasts run all over your body and crush you from all side.
Every moment a new hit, a new injury, getting inflicted on your body, so much pain in so little time that even an awakened human's brain start legging and failing to comprehend.
That's what Rio reminisced about as he closed his eyes.