Not old magic, dark magic. There are many mysteries to the dark forces that are in Equestria, but one thing is for sure, some of the magic is very dark, and that magic looks the coolest. Sure some super powerful beings can fight it off, and some forces of good and light can produce the dark magic too, but generally we can assume it is used for dark deed that most cannot handle.
Draw anypony you want casting or fighting it, or just having their eyes taken over by the evil darkness.
You have 30 minutes to draw, then 15 minutes to submit! Have fun!