Why can't we pray for the conversion of the Devil?

I can't think of a lonelier guy, can you? Here is a fella who made the ultimate blunder in trying to take over Heaven and loses. But, he loses not for the day but FOREVER! Wow! What a horror! I'm sure he is just a very misunderstood narcissist. His ego must be quite deflated by now. Maybe a few prayers to cool the flames of anger between Lucifer and the Holy Trinity can get everyone to play nice again. What do YOU think?