Xen Yang, the Dragon Emperor is the ruler of the empire of Cathay, the largest nation in the world. He rules over a vast empire of many different peoples and cultures and his subjects number untold millions [1a][1b].
He and his wife, the equally revered Moon Empress spend their time in the Celestial City above Wei-Jin where they contemplate the destiny of the empire. They are immortal Dragons who can also take humanoid form. 
The Emperor has nine children who rule the mortals, although four have been lost over the ages. 
- Li Dao, the Fire Dragon, Ruler of the Southern Provinces, he defends the border of Cathay with Ind and Khuresh. 
- Miao Ying, the Storm Dragon, ruler of the Northern Provinces and Commander of the Great Bastion. 
- Shen-Zoo, Bringer of Light and Hope.
- Yin-Yin, the Sea Dragon, she rules the Eastern Provinces and is Admiral of the Grand Dragon Fleet. 
- Yuan Bo, the Jade Dragon, administrator and ruler of central Cathay. 
- Zhao Ming, the Iron Dragon, ruler of the Western Provinces and Lord of Shang-Yang. 
- The Spirit Dragon is rumoured to lie within the Dragon River. 
He and his Empress existed when the planet was colder, before even the Old Ones came and pulled it closer to the sun. 
In 1999 IC the Emperor and his wife vanished, leading to the Time of Darkness and Disharmony when their children fight amongst themselves and the Monkey King becomes Emperor  in 2377 IC. 
The Emperor and Empress return in 2380 IC and cast down the Monkey King. 
Old World information
Scholars outside Cathay understand that his full title is Celestial Dragon Emperor[1a][1b]; another of his titles seems to be Monkey King. They understand that the Dragon Emperor is supposedly immortal [1a] and that some believe that he is an actual dragon in the form of a man [1b].
- Emperor Xen Houng ruled around - 2748 IC, shortly before the creation of the Great Maw.
- An unnamed Dragon Emperor unified the land of Cathay into a single empire in - 1800 IC. He ordered the construction of the Great Bastion, a gigantic fortified wall, to protect his new empire against the marauding tribes of the Hung.
- Emperor Wu, of the Wu dynasty, was crowned in 1676 IC[*]. In reality, Wu simply means Magical lord. In 1690 he sent a large fleet to invade and conquer the Southlands[6a][6b]. The invasion ended in utter failure. It was probably this same Emperor Wu who met a large Tilean expedition in 1699 . In the end he hired its members to protect the western borders of his empire against the Hobgoblin hordes.
*Warhammer Armies: Lizardmen (5th Edition)[6a] reports that the Cathayan invasion of the Southlands was launched in 1690 IC, the fourteenth year of Emperor Wu's reign.
- 1: Warhammer Rulebook (7th Edition)
- 2: Red Thirst (Short Story)
- 3: Warhammer Armies: Ogre Kingdoms (8th Edition), pg. 22
- 4: Warhammer Armies: Ogre Kingdoms (6th Edition), pg. 8
- 5: Warhammer Armies: Warriors of Chaos (7th Edition), pg. 38
- 6: Warhammer Armies: Lizardmen (5th Edition)
- 7: Warhammer Armies: Dogs of War (4th Edition), pgs. 85, 92, 93
- 8: Total War Blog
- 9: Interview with Andy Hall, Warhammer 3's Lead Writer
- 10: Total war Blog Lore roundtable
- 11: Total War Warhammer III