I believe it is the Holy Roman Empire was one of them which took place in 950–1200 and Carolingian Empire which took place in 800–888
The Holy Roman Empire was regarded as one of the earliest roots of the European government because they had one of the earliest forms of democracy. I'm not sure about the Carolingian Empire but I think they were significant. I hope this helped
Slaves were expected to work for as long as the sun was shining. 10 to 16 hours of hard work were imposed on slaves who had to make sure their masters’ crops were taken care of. The slave was at the disposal or even at the mercy of his master.