"Remove the thoughts about betraying me out of your head and the pain will subside"
After torturing him for a good 15 minutes, Nux suggested.
After what could be said the worse pain he ever experienced, Alger heard Nux's next words and quickly did as he was told.
Actually, Nux found out that once the pain starts, the target doesn't have the time to think about betraying him or anything along those lines since the pain is already too much.
The requirement is to be loyal to him. Once the target thinks about being loyal to him, the pain will subside.
Of course, when assaulted with that level of pain, no one would be able to think about anything, and the pain will continue until someone tells the target to be loyal to Nux.
Nux could stop the pain, but he wanted to torture him a little as a punishment for attacking Edda and Fel.
'Haah… haa… haahh…'
Alger breathed heavily after the pain subsided.