The medicine applied to Zhang Tie’s legs was brought by Captain Kerlin. Every two days, Captain Kerlin would visit Zhang Tie and would drop off a small packet of medicinal powder, which was to be applied to his wounds. Unknown whether it was the effect of the powder or the small tree in the Castle of Black Iron, Zhang Tie discovered that the recovery of the wounds on his legs was truly fast. By the second time he applied the medicinal powder to his wounds, Zhang Tie already did not need to use a crutch to walk. Six days later, when he applied the medicinal powder for the third time, Zhang Tie was already able to run.