I'm writing a fantasy book which relies a lot on history, most precisely Roman Empire and The Great Tartaria. I'm already investigating this topic, but I would like to read about the knowledge y'all may have about what was The Great Tartaria, what was its territory, what happened to it, what does it have to do with Roman Empire.

Any information you have about this, would be very useful.

P.S. I'm aware it's not approved by historian communities and stuff, all I wanna know it's what is it known about this just so I can get it into my story