What must you agree to do if you are to join Tom Sawyer's gang?

Tom says that,"Everybody that wants to join has got to take an oath, and write his name in blood.” They must also keep gang all secrets. In addition,

"If anyone else harmed a boy in the gang, then the gang would choose one of its members to kill that person and his family. The boy would not be allowed to eat or sleep until he’d killed them and hacked a cross on each of their chests—the cross being the sign of the gang. "