i heard that the production team cast over 350 actors for this drama...

First Appearance/Mentioned

Episode 1: Shi Jingtang, Yelu Deguang, Zhang Yanze, Zhang Huaishu, Zhang Shi, Zhao Hongyin, Zhao Kuangyin, Shi Chonggui, Feng Dao, An Chongrong, Du Chongwei, Qian Hongjun (eldest prince), Zhou Ping, Hu Jingshi, Qian Yuanguan, Yuan Dezhao, He Chengxun, Shen Wenqi, Marshal Dai Yun, Du Zhaoda, Cheng Zhaoyue, Qian Hongchu, Lord Yuru, Li Yuanqing, Third Prince (Qian Hongyou), Qiang Hongzuo, Qian Hongchu, Steward Hou, Xue Wen, Lady Yu, Zhu Wen.

Episode 2: Yu Wenxiu, Sun Taizhen, A You, ShuiQiu ZhaoQuan, Yan Tong, Lady Wu, Huang Wei, Hu Jing, Sun Tingfu (mentioned only , father of sun taizhen), Qian Hongzong (7th prince), Crown Prince (mentioned only, 5th prince), Liu Yanchen.

Episode 3: Jinding (mentioned only, The Third Prince's maternal aunt and the wife of Marshal Dai Yun), Wen Xiu.

Episode 4: Qian Yuanyi (prince of jinhua), Fan Zhi, Lady Li, Marshal Jing (mentioned, unknown name, perhaps Jing Yanguang?), Shi Chongrui (7th prince), Feng Ji, Sang Weihan.

Episode 5: king Wenmu (mentioned only), He Zhen, Liu Zhiyuan, Li Keyong (mentioned only), Yang Guangyi, Zhang Yanze.

Episode 6: Yao Yuanfu, Zhao Kuangyi, the wife of Zhao Hongyin (mentioned only, surnamed Du, given name unknown), Zhao Kuangmei (mentioned only, unborn), Shi Shouxin, Jiang Ping, Zhan Nan, Guo Rong (Jungui), Guo Wei (mentioned only).

Episode 7: Fu Zhuer, Yelu Jieli, Xue Juzheng, Lu Yin (aka Yuqing), Xu Dingchen (aka Xu Xuan), Ziping, Sang Guoqiao, Yang Guangyi, Liu Qingyi, Liu Tingrang, Liu Shouzhong, Wang Zhengzhong, Wang Shenqi, Li Jixun, Han Chongyun.

Episode 8:  Lady Ding (lady of Chu State)

Episode 9: Yelu Xieli

Episode 10: Gao Xun (mentioned only), Shixiong (mentioned only), empress dowager Li, Wuyu (future emperor of Liao according to wiki), Zhang Li, Zhang Miao.

Episode 11:  Lady of Ning (mentioned), Lady of Zhao (mentioned), Yelu Ruan (prince of yongkang), Yelu Wuzhi.

Episode 12: Shi Hongzhao, Su Yugui, Yongde, Liu Chong, Liu Jiye, Yelu Talie (mentioned), Yang Hongxin (mentioned), Zhe Sanlang (mentioned), Xiao Siwen (son in law of yelu deguang, mentioned), empress dowager lady Shulu (mentioned), Wang Jun, Wang Xiufeng, Su Yuanxi, Wang Qiong, Yelu Langwu (mentioned).

Episode 13: Yelu Licha, Shen Yin(Huzi), Shen Chongyue, Fang Hongjin, Chen Xing, Du Hao, Gao Xu, Cui Renji, Zipan. 

Wow. Thanks so much!!