The Middle Hierarchy are the Dominions, Powers and Authorities.
The Dominions
Colossians 1: 16
For by Him all things were created that are in Heaven and that are on Earth, visible and invisible, whether Thrones or Dominions or Principalities or Powers.
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The Dominions serve God with joy and hold dominion over the Angels who follow them. They send down on Earth power for wisdom to govern well, and the Dominions teach us to subdue our senses and sinful impulses and to subject our flesh to the spirit.
The Powers
1 Peter 3: 22
Who has gone into Heaven and is at the right hand of God, Angels and Authorities and Powers having been made subject to Him.
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The Powers give the Grace of Wonderworking to Holy men and women living close to God. They encourage Spiritual strength to us all who struggle to live God’s Will and to fight against the passions and conquer everything evil. The Powers also assist us in patience and fulfilling obedience.
The Authorities
1 Peter 3: 22
Who has gone into Heaven and is at the right hand of God, Angels and Authorities and Powers having been made subject to Him.
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The Authorities have authority over the devil. They protect people from demonic temptations and prevent demons from harming people as much as they would like to. The Authorities also help Ascetics and righteous people in struggling against evil thoughts.