Following the destruction of the Leir Empire, much of their former territory was left a barren desert. With the general lack of fertile land and readily available sources of water, human inhabitation became nearly impossible save for the hardiest of travelers. What thrived in its place were automatons leftover from Leir - both servants and soldiers.
One of the factions that rose up was the Iron Sisterhood, a series of powerful, next-generation mechanis that were in mass production in order to defeat the Second Heilinthar Empire. They were designed to be long-lasting, resistent to the elements, and reputably nigh-invulnerable. Even hundreds of years after Leir's destruction, they remain incredibly resilient and undeterred by wear and tear.
After Leir's destruction however, these mechanis were left without purpose. Thus, they came up with their own. The Iron Sisterhood, when they were originally programmed, were given the directive to bring peace to the Leir Empire. With the Leir Empire gone, they interpreted it as bringing peace so that no one could ever experience the horrors of war again. And thus, they became traveling assassins and enforcers.
The former territory of Leir saw a reignition of violence and chaos as the Iron Sisterhood attacked and razed anything they considered a threat to peace. They are responsible for slaughtering entire noble family lines in kingdoms they saw as corrupt. The Iron Sisterhood prides themselves in thinking for the long term to supposedly prevent history from repeating itself.
In the post-apocalyptic time of Leir's aftermath, the Iron Sisterhood is one of the most dangerous threats in the desert.