[Mariner]

The Golden Horde:

https://en.wikipedia.org/wiki/Golden_Horde

Predates the first Tsar of Rus

https://en.wikipedia.org/wiki/Tsardom_of_Russia

By 300 years.

[WilliamWallace1999]

Only use of the word Tsar to describe their autocrat.

Read a tiny bit about Basil II, his battle with the Fatimid Caliphate, war with the Bulgars, alliance with the Rus, campaign against the Khazar Khaganate, and spread of Orthodoxy into Russia. The concept of autocratic rule took root in this part of the world a bit before the Golden Horde.

Then review the Byzantine-Mongol alliance. There is a reason the byzantine became and adjective when describing convoluted diplomacy.

Finally check out:

Byzantium and the Rise of Russia: A Study of Byzantino-Russian Relations in the Fourteenth Century Paperback – March 5, 1997
by John Meyendorff