Warriors Orochi 2 - Wu Chapter 3 - Battle of Nan Zhong | Crystal Treasure Guide

To get the Crystal treasure, you just have to trigger both Meng Huo's fire attacks and defeat Pang Tong. Pretty easy, just remember to wait for Meng Huo to light the enemy up after defeating Cao Ren and double back for Pang Tong when he reappears.