Can you change from good to evil in adventure quest worlds?

yes. what you do is as you are playing and when yo go to somewhere you write down the /join (the room name here) after you do that you can go back to it later even in the castle where you get to choose you can go back a re pick which side you are on- I hope that helps, i have both stuff from good and evil, it worked for me

It's /join castleundead

something like that

It costs 100,000 switching from evil to good. I don't know about good to evil. Go to Shadowfall and talk to that queen.