How do you get to the grox in spore

they are towards the center of the galaxy guarding the galactic core. i don't know any way to befriend them so you will have to fight them unless you are clever enough to please them (if its possible). they always colonize terrascore 0 planets. i tried improving their planets and placing embassies but they hate that so dont try it before taking them on i suggest getting max health and all the weapons from a satisfied spore gamer