To obtain this Achievement you will first need the Queen Goat Mutator because it has the ability to summon dead goats. You get this by scaling the small tower near the game spawn and hoping inside the top window, once inside the castle make your way to the throne and jump up on it. After a few seconds you'll be warped back to the area and have the Achievement for Queen Goat and the Mutator.
Make your way up to the end of the map where the boulder is near the red building and you'll see a trail that leads to a sacrifice ground. Once inside and with the Queen Goat Mutator equipped press
5 times inside the pentagram and Goats will fall from the sky, if like me only 4 drop go and grab a human with
and they will work to make up 5. Once this is done you'll get the Achievement after a freaky thing happens with the bodies.