anyone that plays minecraft: twilight forest mod help!

[tools guy-kun]

I see these big giant castles around, but whenever I try to mine a block to get inside, it doesnt break the block and theres a green barrier around the castle. I tried using creative, and I was able to get in, but I was unable to kill, or even hit the hostile mobs inside, and I still wasnt able to break a block inside as well!! How can I have full access into a giant castle??

[t]

You have to do the progression. Google it or look at the achievement list.