Power against demons is faith against demons (Matthew 10:1,8. Lectures on Faith).
Priesthood is not power; it is authority.
Priesthood is the authority to gather. It is to preside, teach, direct. It is the government of God. It is a divine commission of service. It is a master/servant relationship. As you serve “faithfully”, you will be filled with faith, which is power, which cometh from above, which causeth them below to turn to them above, that bringeth honor up on high.
Priesthood of the Aaronic order officiates in the earthly, outward of the flesh-commandments, ordinances, judgements, curses (D&C 84:26-27, 107:20). Heavenly priesthood, that which is of the order of the Melchizedek, operates in the earthly and heavenly spheres; blessings and commandments (D&C 84:19-22 , 107:18-19). Melchizedek reveals commandments, while Aaronic teaches them. Aaronic does that spiritually which is of necessity physical. Melchizedek demonstrates that which is physical, to accomplish the spiritual. Both Aaronic and Melchizedek are authorized to expound the scriptures by the Spirit, which is the Word, which is the only true authority, the Priesthood.
If you are faithful as an outcast, whereby ye became a servant, if you continue in loyalty, you will become a son. If your love is full ye shall by and by be a friend. Friends are of equal treatment (not status), and thereby all are one, one being in all. You must be fully light, or fully dark to be one; otherwise ye are but parts, confused and unsatisfied in life.
Faith is a gift, as are Charity and Hope. Faith is power produced by loyalty, and comes by hearkening to the Word of God, and is nurtured through prayer. It is the assurance of things hoped for, the evidence to which is not yet come to pass. Faith is acting according to truth. Faith is the desire to please God. Charity is being filled with the desires of God. Hope is the promises of God, which fill you with confidence, which adds to your faith, which is made fruitful through charity, which possessing, you are given greater promises; with which your faith expands, and your knowledge evolves.
We are saved by our faith and works, God’s grace and mercy, and Christ’s blood and mediation. Contrary to many Mormon views, we are not saved by knowledge; that is gnostic doctrine. However, we do gain knowledge from God as a result of our salvation.