The priests had a lot of power, a long with being smarter than most, like being literate. This sure would you give a lot of power by itself at this time, most others not being literate but you being one of the few that are literate.
The kings also had lots of power. They gave knights and lords land, whether the land was taken or not. It was the serf homes that were taken especially when land was taken. The lands cost was loyalty and to be called in at any time for knights, the cost for lords are soldiers/knights.
Lords have high power, not as high as Kings and Queens, but above Knights. They got the King and Queen soldiers in exchange for land.