The land of Al-Hind, on the far banks of the great river Indus, is mentioned briefly in The Cradle and the Crescent as a possible destination of merchants, the source of over-sized fantastic elephants and a place of many other marvels. There are vague references to the Mythic Muslim holdings of al-Sindh on the near banks of the Indus but much of this material was later cut.
Mythic India is deliberately not mentioned.
This is because it does not exist.
Just because a realm or continent exists in the real world does not mean it exists in the world of Mythic Europe, although there may be fantastical traveler’s tales about an equivalent. This was intentionally done for a number of meta-game reasons that have to do with the nature of the boundaries of the world of Mythic Europe.
In the thirteenth century much if not all of the knowledge of far off realms and kingdoms fits more accurately into stories than fact, making them if not part of Faerie itself, then at least better contained within Faerie regiones rather than occupying a set geographic locale in the mundane realm. For example, North America does not canonically exist in the world of Mythic Europe, but Greenland and Vinland do, although the latter or both may actually be a Faerie Realm reached via crossing over the mundane western limit of the Great Ocean. Similarly the Line Editor has stated clearly that there is no Mythic China, but there are many tales of Serica, the land of Silk, and these stories breed and change through dispersion and the influence of Faeries that encourage travelers to claim they have journeyed from such a place. There are thus many different and varied Sericas, each dependent on the traveler, allowing a multitude of stories to coexist.
Travelers claiming to have visited these fabled lands may just be base liars using the stories for their own profit, they may be fools deluded by their travels into Faerie regiones or sections of Arcadia with motifs that mirror real world China, or they may even be Faeries posing as travelers and living out a role that fulfills their own story of imaginary lands to the East. The truth is less important than the potential for adventure.
This approach allows characters to participate in stories about these lands without having to deal with the enormous detail required to do justice to such complex societies and kingdoms such as India and China. Each visit can differ from the last one and the experiences may even contradict each other, but this can all be explained by the fluctuating nature of Faerie.
In effect there’s an imaginary and shifting line stretching along the Indus river into the mountains, passing through the Pamir knot and then the sands of the Taklimakan Desert just beyond Khashgar that extends northwards into the Mythic Steppe somewhere to the east of the battlefield of Talas. This line marks the edge of the map as it where, the point beyond which the mundane lands of the world of Mythic Europe fade into myth and fable, Magic and Faerie.
This is not to say there can’t be pockets of mundane geography further east, but these pockets are like islands of fact amidst a sea of roiling fiction beset with waves of stories that lap against the shores of reality or break upon the edge of Mythic Europe, flooding them with adventure.