So this DLC introduces China as an off-map entity which you can ally with or war with. Being in the good graces of the Emperor grants you bonuses you can request, such as wives, scholars, generals, artifacts, etc. It also introduces the ability to write books, which function as artifacts to give your characters a boost. There are new Casus Bellis as well, giving you more ways to go to war.

Playing as any of the older easter factions, be it nomadic Mongols, variety of Indian rulers or outright the newly added Tibethian culteres the game will run differently with the Chinese Emperor ever watching towards it's western borders and protectorates.
New retinues, especially the Tibethian mountaineers bring forth new tactics, you might not assume 100 LC and 400 LI make a good retinue, but you might be surprised. The Chinese honor guard is also a fun little force you can raise for free.

This DLC is a nice addition with some decent features added into the game. That said, it is not a necessary addon for how I typically like to play. Taking that bias out of it, I rated it with 4-stars