Yi Ti is a nation and region in Essos located east of Qarth and the Bone Mountains and bordered by the Jade Sea to the south. Nearby islands in the Jade Sea are Leng and the Isle of Whips. North of Yi Ti are the Great Sand Sea, the Shrinking Sea, and the Bleeding Sea; a great river runs south from the Bleeding Sea through Yi Ti to the Jade Sea. Located east of Yi Ti are the Mountains of the Morn, the Shadow Lands, and Asshai. In the Common Tongue, things relating to Yi Ti are known as "YiTish".
The realm of the YiTish civilization is known as the Golden Empire of Yi Ti, which was, according to legend, preceded by the Great Empire of the Dawn. Maester Yandel speculates the YiTish civilization was contemporary with the realm of the Fisher Queens, whereas the YiTish priests insist that mankind's first towns and cities arose along the shores of the Jade Sea, dismissing the rival claims of the Sarnori and Ghiscari as the boasts of savages and children.
Lomas Longstrider called Yi Ti "the land of a thousand gods and a hundred princes, ruled by one god-emperor." The power of the God-Emperor has since fallen and extends no further than the walls of his own city, but the hundred princes rule their own realms as they see fit, as do the brigands, priest-kings, sorcerers, warlords, imperial generals, and tax collectors outside their domains.
The land of Yi Ti has thick, green patchwork farmland and a verdant rainforest. Rumors have it that basilisks roam the jungles of Yi Ti. Known cities in Yi Ti include Yin and Jinqi, along the Jade Sea coast, and Tiqui further to the north near the Great Sand Sea. The city of Asabhad is located at the western boundary of Yi Ti near the Bone Mountains and the Jade Gates. There is a trade route from Asabhad to Yin along the coast of the Jade Sea. The Five Forts guard the northeastern marches of the empire.
Yi Ti is ruled by a god-emperor, but true power may reside within the region's various princedoms. It has had various ancient capitals, including Tiqui. The Lion of Night is a god in Yi Ti. One of their major exports is saffron. Traders from Yi Ti travel to Vaes Dothrak to trade. Wines from Yi Ti can be found as far west as Pentos.
According to scribes of Yin, all the lands between the Jade Sea and the Shivering Sea, the Bone Mountains and the Grey Waste were all part of the Great Empire of the Dawn and fell under the control of the God-on-Earth, the only son of The Lion of Night and the Maiden-Made-of-Light. He is said to have had a hundred wives and to have reigned for ten thousand years, before ascending into the stars to join his forebears. He was succeeded by his eldest son, the Pearl Emperor, who ruled for a thousand years. He was followed by the Jade Emperor, the Tourmaline Emperor, the Onyx Emperor, the Topaz Emperor, and the Opal Emperor, who all reigned for centuries. Each successive ruler had a shorter reign and faced rising problems, as mankind grew greedy and corrupt.
The Opal Emperor was succeeded by his daughter, the Amethyst Empress. Her younger brother slew her and usurped the throne, and event which is remembered as the Blood Betrayal. He proclaimed himself the Bloodstone Emperor and began a reign of terror, practicing dark magical arts and necromancy. He cast down the true gods to worship a black stone which had fallen from the sky. According to the annals of the east, the Blood Betrayal is attributed as the cause of the Long Night, as it caused the Maiden-Made-of-Light to despair and turn her face away from mankind, while the Lion of Night sent the generation-long winter to punish mankind. In the chaos that followed, the Great Empire of the Dawn collapsed.
The maesters of the Citadel in Oldtown doubt that the Great Empire of the Dawn ever truly existed, but most do agree that Yi Ti's culture is very ancient, and a few believe they were contemporary with the Fisher Queens on the western side of the Bone Mountains.
Yi Ti was one of the first civilizations to develop and preserve a literate culture. Since the Long Night, eleven dynasties of emperors have ruled over Yi Ti. Some of them ruled no more than half a century, while the longest ruled for seven hundred years. Sometimes the transition between dynasties was peaceful, but other times it was violent On four separate occasions, the end of one dynasty did not immediately result in a new one that had consolidated rule over all of Yi Ti, but prolonged periods of civil war and anarchy - the longest of these interregnums lasted more than a century.
Each of the imperial dynasties that have ruled Yi Ti were known by a color honorific, i.e. the current dynasty at the time of the War of the Five Kings in Westeros are known as the line of "Azure Emperors". The names of all eleven dynasties are known, but Yandel did not specify their exact order.
The original capital city of Yi Ti was Yin, at the mouth of a great river on the shores of the Jade Sea. It is a massive and advanced city, whose imperial palace alone is the size of all of King's Landing. The capital was moved to several other cities, then moved back to Yin, then moved again over the millenia, as different dynasties rose and fell. Under the Azure Emperors, the capital is once again in Yin.
Yandel gave two brief listings of emperors which may or may not indicate the order of the eleven dynasties. First, explaining how the capital has moved: the Grey Emperors, Indigo Emperors, and Pearl White Emperors ruled from Yin, but the Scarlet Emperors rose a new capital from the jungles, called Si Qo (which fell into ruin after that dynasty ended); the Purple Emperors ruled from Tiqui in the western hills (bordering the formidable Hyrkoon cities of the mountains), while the Maroon Emperors had their capital in Jinqi to the east, to guard against raiders from the Shadow Lands. This is the order that Yandel gave this information, but whether it necessarily means that (for example) the Scarlet Emperors predate the Purple Emperors, is unclear.
Second, Yandel then gave a brief listing of several notable emperors - though whether he presented them in the order of their dynasties, or simply by their individual noteworthiness, is unknown. He began by listing Har Loi, the first of the Grey Emperors, then Choq Choq, fifteenth and last of the Indigo Emperors - seeming to match the order of the first list he gave, which also began with Grey, followed by Indigo. The listing then mentions Mengo Quen, third of the Jade-Green Emperors, then several of the Scarlet Emperors, and only after them mentioning the Nine Eunuchs of the Pearl-White Emperors - whereas in the original listing, he mentioned the Pearl-White Emperors before speaking of the Scarlet Emperors. The listing then says that Yi Ti reached the apex of its power under the Sea-Green Emperors, who conquered Leng, as well as Great Moraq, and exacted tribute from Qarth, Old Ghis, and Asshai, and traded with Valyria. He then mentions that Chai Duq, the fourth Yellow Emperor, took to wife a noblewoman of Valyria, and kept her dragon at his court.
Some of these dynasties can be vaguely dated by mention of their interaction with foreign peoples: both the Sea-Green and Yellow Emperors were in trade contact with Valyria, which only rose as a power some 5,000 years ago, so these probably weren't among the earliest dynasties closer to the Long Night. It is outright said that the line of Yellow Emperors died out about one thousand years ago. Meanwhile, the long line of Scarlet Emperors ended when the forty-third and last of them, Lo Bu, was killed in his devastating war against the Jogos Nhai to the north - and it is elsewhere said that the Jogos Nhai have been warring against Yi Ti for the past "two thousand" years, putting the Scarlet Emperors in that timeframe.
Apart from the wars against the Jogos Nhai, the second dated event mentioned is that the island of Leng threw off the control of Yi Ti about four hundred years ago - which would put it around the time of the Doom of Valyria, though whether that has any significance is unknown. The loss of so much territory might have been related to the fall of a dynasty, possibly the direct predecessors of the Azure Emperors (four hundred divided by seventeen yields an average reign of twenty-four years, which is certainly plausible).
The ruler of Yi Ti at the time of the War of the Five Kings is Bu Gai, the seventeenth Azure Emperor. Exactly how this dynasty originated is unknown. Given that the longest dynasty lasted 700 years, and the Yellow Emperors died out "a thousand" years ago, there must have been at least one intervening dynasty between them and the Azure Emperors. Moreover, it is said that Leng was alternatively ruled by Yi Ti's emperor in Yin or Jinqi, which was the seat of the Maroon Emperors (though perhaps not exclusively that one dynasty). Thus it may be possible that the Yellow Emperors were followed by the Maroon Emperors, whom Leng revolted against, after which the dynasty of Maroon Emperors collapsed and were replaced by the Azure Emperors.
Ultimately, despite these scattered clues, the exact sequence of dynasties is simply unclear.
The Azure Emperors, by the time of Bu Gai at least, have become comparatively weak. Their rule over all of Yi Ti is largely nominal, while in practice the local governors and tax-collectors have carved out a hundred different princedoms among the provinces. Moreover, a general on the northern frontiers with the Jogos Nhai has openly taken on imperial honors, proclaiming himself the first "Orange Emperor", with his seat at the crude military post known as Trader Town. It is also rumored that a sorcerer claiming to be the last Yellow Emperor has come to rule over strange Carcosa, far to the east of Yi Ti itself, where he is gathering strength to one day reclaim rule over it.
A Game of Thrones
Daenerys Targaryen remembers that basilisks infest the jungles of Yi Ti. In the Western Market of Vaes Dothrak Dany sees a fat cloth trader from Yi Ti haggling with a Pentoshi over the price of some green dye, the monkey tail on his hat swaying back and forth as he shakes his head. 
Before Khal Drogo's body is burnt on his funeral pyre Ser Jorah Mormont begs Daenerys Targaryen to come east with him, to Yi Ti, Qarth, the Jade Sea and Asshai-by-the-Shadow, to see all the wonders yet unseen. 
A Clash of Kings
In Qarth Xaro Xhoan Daxos tries to entreat Daenerys to accompany him on his pleasure barge to the Jade Sea. He suggests that they journey around Yi Ti to search for the dreaming city of poets and to sip the wine of wisdom from a dead man's skull.
A Storm of Swords
A Feast for Crows
A Dance with Dragons
- The Lands of Ice and Fire, The East.
- The World of Ice & Fire, Yi Ti.
- The World of Ice & Fire, Leng.
- The World of Ice & Fire, The Bones and Beyond.
- The World of Ice & Fire, The Bones and Beyond: Yi Ti.
- A Game of Thrones, Chapter 23, Daenerys III.
- George R. R. Martin's A World of Ice and Fire.
- A Feast for Crows, Chapter 34, Cat Of The Canals.
- A Clash of Kings, Chapter 40, Daenerys III.
- A Game of Thrones, Chapter 36, Daenerys IV.
- A Game of Thrones, Chapter 54, Daenerys VI.
- A Dance with Dragons, Chapter 1, Tyrion I.
- The World of Ice & Fire, Jaehaerys I.
- A Game of Thrones, Chapter 72, Daenerys X.
- A Storm of Swords, Chapter 71, Daenerys VI.
- A Feast for Crows, Chapter 21, The Queenmaker.