It's rare that a slave gets to lick Katie without some sort of pain element attached. That's because licking her womanhood is the ultimate reward for any slave, therefore it's natural that a slave must suffer to earn it. Katie likes to use the cock shocker on slaves that orally pleasure her because it serves the dual purpose of reminding him that he must suffer to earn her pussy, and because as it turns out slaves lick better when their cock is being electrocuted. So it's win-win all around.