On day 10 as Bachelor, Mark the Immortal tells me about a wierd ritual somewhere in the steppe, but I can´t find the place.

I checked the english walkthough, which has a picture of the place (the quest is called "Chimaeras. Pictogram"). On the picture, you can see that the place is near the town (you can see houses in the background), but I still couldn´t find it.

I found a place where a Odong asks me if I want to fight a battle of life or death without weapons, where I can win a phiole of blood, but that doesn´t look like the place pictured in the walkthough.

Yep, that's not it. The place you're looking for is located on the line between the Abbatoir and Stamatin's - there's a closed yard between the houses, just use the right hand method to find the entrance - inside you will see the Auroks on a bone pole stiking out of the ground and lot's of people led by a shopkeeper-like looging guy. Talk to him.

Found it!