https://en.wikipedia.org/wiki/Feodosia#Kaffa_(Genoese_colony)
In the late 13th century, traders from the Republic of Genoa arrived and purchased the city from the ruling Golden Horde. They established a flourishing trading settlement called Kaffa, which virtually monopolized trade in the Black Sea region and served as a major port and administrative center for the Genoese settlements around the Sea. It came to house one of Europe's biggest slave markets. The Great Soviet Encyclopedia also adds that the city of Caffa was established during the times when the area was ruled by the Khan of the Golden Horde Mengu-Timur.
Ibn Battuta visited the city, noting it was a "great city along the sea coast inhabited by Christians, most of them Genoese." He further stated, "We went down to its port, where we saw a wonderful harbor with about two hundred vessels in it, both ships of war and trading vessels, small and large, for it is one of the world's celebrated ports."
https://en.wikipedia.org/wiki/Crimean%E2%80%93Nogai_slave_raids_in_Eastern_Europe
For over three centuries, the military of the Crimean Khanate and the Nogai Horde conducted slave raids primarily in lands controlled by Russia and Poland-Lithuania as well as other territories.
Their main purpose was the capture of slaves, most of whom were exported to the Ottoman slave markets in Constantinople or elsewhere in the Middle East. Genoese and Venetian merchants controlled the slave trade from Crimea to Western Europe. The raids were a drain of the human and economic resources of eastern Europe. They largely inhabited the "Wild Fields" – the steppe and forest-steppe land which extends from a hundred or so miles south of Moscow to the Black Sea and which now contains most of the Russian and Ukrainian population. The campaigns also played an important role in the development of the Cossacks.