Amon helped Xin Wuming prepare the Thousand-Year Mandrake. He boiled it until the mandrake's poison was gone. He then handed it to Xin Wuming.
Xin Wuming knew what this Thousand-Year Mandrake could do. He was stunned that Amon had the mandrake. He was sure that Amon had gotten this mandrake from the secret dimension. What puzzled him was, how did Amon smuggle such a valuable thing past the White Cloud's inspection? Furthermore, Amon even gave such a valuable treasure to him. He was extremely touched by this. He knew then that following Amon was indeed the correct path.
Xin Wuming consumed the mandrake without hesitation. Amon wanted Wuming to do it right here because if he took it back to the clan, there was a chance of the mandrake being discovered and taken by someone else in his clan.
After finished consuming the mandrake, they just sat there and waited silently.