I have a quest to take a Tatar prisoner to Sich. I took the prisoner to Sich and was told to take him to the Ataman. There is no location or character named Ataman, and nothing happened when I went to the person who owns Sich. The Quest just says that we have to go to the ataman.

Does anyone know where to go from here?
Thanks

Thanks for the fast reply! I actually tried going to the owner of Sich and there was no special dialogue option.
I'll try going to the faction leader now.
One thing that's strange is that in my game, Sich is owned by the Crimean Khanate and they are currently at peace with the Cossacks, but the quest assumes both that Sich is owned by the Cossacks and that the Cossacks are at war with the Khanate.

In that case, if going to Khmelnitsky doesn't work:

the quest may be temporarily broken - AFAIR it does sometimes happen that story quests require conditions that don't actually exist on the map (extreme case: the hero is asked to capture the Russian Tzar.. after the faction has been eliminated, no solution exists).

I'd talk to all the lords of the Cossacks and check for that option (the game might remember who was the last Cossack owner of that town). If that doesn't help, consider provoking a war between the Cossacks and the Crimean and helping the Cossacks take Sich.

So I tried going to the original owner of Sich (the Cossack who no longer owned it) and he allowed me to continue the quest.