Thy Rod and Thy Staff
lucifer has to know words to keep the sinners in their tiny boxes
Lucifer knows words—a gift and a curse, but he is thankful all the same. Knowing words means having power, and even though he is the sole king of the sinners, having power means he can't be threatened. Sinners are greedy are lustful are little boxes that hide large grand schemes.
Sinners are human, and they always work for themselves, only.
But Lucifer is intellectual is king is fallen angel who leapt too soon; he knows what power is, what words mean and how it feels to bend to another's will. He knows how to use their sins to his advantage—to keep them in their tiny boxes with no way out.
(Sometimes, they speak back, except not with words, but Lucifer is always willing to learn.
Soon, his fingers work as well as his tongue.)