For the PK Circle AKA: Martial Arts Circle, you must undergo a quest that doesn’t take very long.
First, speak to CaptainHe, near the Pet Shop. After hearing him talk, click “I want to apply” option, and you’ll receive a dart. Now, after you’ve recieved the dart, proceed to GeneralCai, who is just north from the Geezer. After you’ve talked to General Cai, you’ll be asked to defeat 5 level 20 Detectives. Once you have defeated all the level 20 Detectives, you’ll be in the circle.
Extra Information: When in the circle, other players can steal your money, harm you, throw darts at you and also kill you. Be advised that you should be of a God/Devil rank before joining, elsewise it will be very frustrating if other people keep knocking you unconcious/sending you to the drug store.
You’re automatically in after you advance to junior god/devil.
How to quit:
You need a lvl 1 Toturtle. To get one, go to the Terryiying Cave 1 and catch a youdragon from there. Now talk to Linda LittleLinda in Tree city. Go to the Eastern Dock and talk with OldFisherman. He sends you to Sword manor. Give LittleYu a Youdragon and he gives you a lvl 1 Toturtle. Leave Sword Manor by talkig to ZhangDing in the entrance and head to the Water city. Find Sage next to the Pawn shop and talk with him. He will send you to Shaolin Library. You can get there by going out from Hill City and then head North-West. Dont go to the bridge, it’s a wrong place. Find Library in Shaolin and talk with MonkBright. A system message will appear, saying you’ve left the circle.