the problem is, it is Polovetsian.

the name of the tribe (?) is polovtsy, but it is a common rule to insert "e" in adjectives from the nouns that end in ts. I guess, we can not pronounce vtsk - this is Check, not Russian. for example, molodcy - brave men. the adjektive
molodetskie...

and the stress is pol-oh-VET-sk -ie as well