I wrote before about the Russian mercenary force in Syria known as "Wagner":
Life of Russian mercenaries in Syria
Spoils of War

However, there is an even more shadowy and mysterious entity also operating there seemingly on behalf of the Russian government - the so-called "Turan" Battalion, which seems to be made up of Muslims from Russia and ex-USSR:

Recently, there were a couple pics of their fighters leaked online, for first time ever

According to one interview, they are connected to Hezbollah in Lebanon:

Their patch, in photo above, is certainly quite similar to Hezbollah patch, only blue, instead of yellow.

Video apparently of Turan ambushing ISIS in the desert, back in July: "Turan" battalion operates against ISIS in the Syrian desert

They are good, these guys, whoever they are. Highly skilled fighters... Precisely what relationship this unit has with the regular Russian military, is thus far unclear...