Killing other people's characters (WITHOUT GODMODDING) is not permitted in the battle ground but may partake anywhere else. When you die you may create new character to be the same race or a different one but if you would like to keep your character you must follow the death system.
Human/ Quincy: When humans/ quincy die they will become either purified souls or hollows. Purified souls will become shinigami and hollows will become arrancar.
Shinigami: When shinigami die they will become hollow or consume the powers of hollows. If you become a hollow then you will become an arrancar but if you consume the powers of hollows then you will become a vizard.
Bounts: When a bount dies they will most likely become hollows but sometimes become purified souls. To become a purified soul a shinigami must kill you and purify your soul. Purified souls will become shinigami and hollows will become arrancar.
Vizards: When vizards die they will either be taken over by their hollow power turning them into a hollow or they will start over. If you become a hollow you will later become an arrancar but if you start over you can choose between being a human, quincy, or bount.
Arrancar: When arrancar die they will either be purified making them purified souls or they will start over. To become purified a shinigami must kill and purify you soul. When you are a purified soul you will become a shinigami but if you start over you will be able to choose between becoming a human, quincy, or bount.