Short answers, pulled from the story.
The Cumans were a Turkic nomadic people from Central Asia who formed the western branch of the Cuman-Kipchak confederation. They spoke the Cuman language and originally inhabited a shifting territory north of the Black Sea and along the Volga River. They entered the grasslands of the present-day southern Russian steppe in the 11th century.
The Cumans spoke the Cuman language, which is considered the best-known of the early Turkic languages. It is attested in medieval documents including the Codex Cumanicus, a linguistic manual written to help Catholic missionaries communicate with the Cuman people. The language was also adopted by Karaite Jewish and Crimean Armenian communities, who preserved documents in Kipchak written with the Armenian alphabet.
After the Mongol invasions of 1237-1240 destroyed the Cuman-Kipchak confederation, Khan Koten led the surviving Cumans to seek asylum in the Kingdom of Hungary. In 1238, King Béla IV accepted them on the condition that Koten's 40,000 families convert to Christianity. Béla intended to use them as auxiliary troops against the advancing Mongols.
The Cumans are believed to have played a decisive role in the uprising led by brothers Asen and Peter of Tarnovo, which resulted in Bulgaria's restoration of independence in 1185. Scholar István Vásáry stated that without the active participation of the Cumans, the Vlakho-Bulgarian rebels could never have gained the upper hand over the Byzantines. At the Battle of Adrianople in 1205-14,000 Cuman light cavalry contributed to Kaloyan's crushing victory over the Latin Crusaders.
The Codex Cumanicus was a medieval linguistic manual written to help Catholic missionaries communicate with the Cuman people. It is one of the primary sources attesting the Cuman language, which is considered the best-known of the early Turkic languages.
After the Mongol destruction of the Cuman-Kipchak confederation in 1241, the Cumans scattered in several directions. Some joined the Mongol Golden Horde and assimilated with local populations. Others fled to the Byzantine Empire, the Second Bulgarian Empire, and the Kingdom of Hungary, where they became integrated into the elite. Some Cuman captives were sold as slaves in Egypt, becoming Mamluks, and some of those Mamluks attained the rank of Sultan. Traces of Cuman settlement remain today in Turkey, Kazakhstan, Ukraine, and northwest Anatolia.