I’ve been looking around, and no one seems to know. Some credit the Cyrus Cylinder saying it banned slavery,some other people say that Zoroastrianism outlawed it, others said it was a decree by Cyrus, but was never enforced, some say it’s just POWs, some say that slaves could convert and free themselves, and so on. So does anyone know, is a there a consensus, and if not, what would be the most likely answer.
Hi, see this discussion as well as this one both featuring me and /u/Aithiopika. In short, there was no attempt at banning slavery in the Achaemenid Empire, but it was not - especially not in the Iranian heartlands - a "slave economy" the way Greece was. Rather, wage labour was the norm, though depending on where you were and what type of labour you needed there may have been exceptions, as with the Babylonian temple slaves.
As for the Cyrus Cylinder, it has nothing to do with this; it is largely just a composition of Babylonian and Assyrian formulaic assertions legitimizing the rule of Cyrus (or rather, "Kurash [II], the king of Anshan"). It isn't a terribly informative document; possibly the most valuable information is it is Cyrus' account of his ancestors which does not include the Achaemenes claimed as the father of Sheshpesh/Teispes by Dareios, suggesting Dareios' claimed kinship with Cyrus and common descent from the patrilineal ancestor of his clan was fraudulent.