The Secret of Tu

"Lord Gongsun's only son is terminally ill. Lady Gongsun refuses to give up on her son. When a magical creature with the power to heal all is sighted, the Lord strikes a deal with the Lady. His nephew Jiang will collect the cure. If he succeeds, their son Bo will take his rightful position as the next Lord. If he fails, the Lady has to accept Jiang as the lawful heir. But when the Lord dies, Jiangs quest becomes a race for his life, as the Lady has no intention of losing her status to Jiang."