Heres a mention of the Tartars:

"The Twisk-landers are banished and fugitive children of Frya, but their wives they have stolen from the Tartars. The Tartars are a brown tribe of Finda’s people, who are thus named because they make war on everybody. They are all horsemen and robbers. This is what makes the Twisk-landers so bloodthirsty. The Twisklanders who had done the wicked deed called themselves Frijen or Franken. There were among them, my brother said, red, brown, and white men. The red and brown made their hair white with lime-water — but as their faces remained brown, they were only the more ugly."

It sounds like the criminals of the white skinned blue eyed peoples stole the Tartar's women and that was the creation of the Franks. The Tartars def. do not sound very impressive lol