I propose Lucifer be given access to two forms from the beginning, where one form is that of of a luminous man, kind of face and beautiful, who focuses on controlling his opponents. His second, more destructive form, would be in the image of the greatest of all the angels. Why should his control form be that of something innocent and beautiful? Because he is the great Deceptor, and looks are certainly deceiving.
The form that focuses on absolute and pure destruction will be called Abaddon, where he calls upon hellfire and the angelic arts in combination with the wielding of his sword to obliterate his opponents. This is his offensive form. The Deceptor form would be more about controlling your opponent, with techniques that would do things like reverse your controls, screw with your camera, do damage to yourself or disconnect you completely. In this form, he need only to whisper into your ear to ensure annihilation.