Black dancing figures on a hill near Shipov Forest

The story isn't very creepy, but it's true. I was about 12-13, born in '89, when we decided to ride with the lads to a kids' camp located nearby. The camp was in Shipov Forest, not deep, almost at the very start, but you had to ride uphill through hills and tree plantations. We saddled up our bikes and set off. Halfway there we wanted to piss, so we turned into a plantation, beyond which was hilly terrain. After doing our business, we decided to pick some wild strawberries and just shoot the shit about stuff. Suddenly Oleg (that's the name of one of my companions) saw something strange on the opposite hill. At first it seemed to me a horse was grazing, but looking closer I realized it wasn't: on the slope of the hill opposite us, some NOE was doing crazy dances, really resembling a horse, only if it had stood up on its hind legs, i.e. in size this fucker was two or three times bigger than the tallest man, was completely black, moved somehow strangely, waving its arms — pretty funny actually. We didn't dare go down from our hill and climb the opposite one closer to the NOE, but for some reason I decided to walk closer to the other slope and saw houses below — the street was almost abandoned, only gypsies lived there. From one yard came something like a prayer, some verses chanted (the voice was loud, as if speaking into a microphone), I remembered only one phrase: "You trade your soul knee-deep in blood." A chill went down my spine from that, but I bricked even more when I saw there were already two NOEs. I shouted to my friends that we had to get the fuck out, and the thing dancing opposite at a decent distance heard it. The two black figures merged into one again and turned 180 degrees. I saw neither eyes nor face — nothing. But I understood that before this the creature had been standing with its back to us, and hearing my voice, it turned around. Then it crouched somehow strangely, as if performing some dance move, some kind of curtsy, and just disappeared. Evaporated. The hill became empty right before our eyes. Then from the other slope of the hill, where the verses were being read, came some shouts of many voices, what they shouted I didn't make out, but we grabbed our bikes and got the fuck out of there as fast as we could. I told my parents about it, but they decided I made it all up. What it was I never understood, sometimes we recall this incident with friends, but none of them has suggested a single version of what it could have been back then.