Stage - Battle of Xinye (Wei) Difficulty - Hard or Chaos Character - Guo Jia
Requirements: Defeat Xu Shu within 8 minutes of starting the battle.
Step 1: Go through the eight gates formation and rescue Cao Ren.
Step 2: Head straight for Xu Shu and defeat him.
As requested here's the unlock guide for Guo Jia's 5th weapon "Heavenly Phoenix" if you have a request feel free to ask and I'll do my best.
Tags: Dynasty Warriors 8 Secret 5th Weapon Unlock Guide Liu Bei Shan Guan Yu Ping Yinping Suo Xing Cai Zhang Fei Bao Zhao Yun Ma Chao Yue Ying Zhuge Liang Kongming Diao Chan Lu Bu Zhu Rong Lu Su Cao Ren Pi Zhou Yu Tai Sun Ce Quan Jian Taishi Ci Zhen Ji Wang Yuanji Ling Tong Lu Xun Meng Huo Jia Chong Xiahou Dun Yuan Ba Zhang Chunhua Wei Yan Han Dang Lianshi Lian Shi