Intention Craft

I was reading chapter 16 when I came across the strangest thing ever. The intention craft. According to the book, it has six legs, looks like a bug, can fly, can turn invisible, can shoot artillery shells out of the air and has other advanced weaponary. What I don't get is, why would a flying machine need 6 legs? I doesn't even use the legs when it flies so what's the point? Maybe I'll find out later...