William is a giant white snake who was originally your servant, but after your uncle, out of greed for power, betrayed your father, then locked you in prison. He was turned into your uncle's henchman, controlled by your uncle and did everything for him. Several hundred years pass and your father tries to break a hole in the prison to help you and your brother get out but is accidentally discovered and you are chased. Your uncle ordered William to bring you back, he turned into a giant snake and chased your brother. Your brother tries to run but is still chased by William

"don't run anymore, you can't escape"