Devil can be used to emphasize what you think about someone or something. For example , if you say that someone is a devil of a nuisance , you mean that they are very annoying . If you say that something is a devil of a problem , you mean that it is a very difficult problem.
speak of the devil
said when someone you have just been talking about arrives unexpectedly
talk of the devil!
used when an absent person who has been the subject of conversation appears
have a devil of a job
to manage to do something, but only after a lot of difficulty
talk/speak of the devil
People say speak of the devil , or in British English talk of the devil , if someone they have just been talking about appears unexpectedly.
have the devil's own job/a devil of a job
If you say that you had the devil's own job to do something or that you had a devil of a job doing something, you are emphasizing that it was difficult to do it.