Todd McLauchlin and Cameron Mayer discuss the crucial role the mission and spirit of Elijah plays in the last days. In many respects, it the essence and end of the restoration, and the lifeline we must take hold of to survive our modern crisis—both individually and as a church—or else the whole earth will be "utterly wasted at his coming" (D&C 2:3). It provides a clear framework in which we can begin to discern true and false spirits, and understand all the doctrine of the restoration.

Cameron Mayer dives a bit deeper into D&C 84 as it pertains to priesthood, temple, and seeing the face of God.

Edit: For one more reference on the "oath" and "covenant" as it pertains to priesthood, consider JST Genesis 14:

26 Now Melchizedek was a man of faith, who wrought righteousness; and when a child he feared God, and stopped the mouths of lions, and quenched the violence of fire.

27 And thus, having been approved of God, he was ordained an high priest after the order of the covenant which God made with Enoch,

28 It being after the order of the Son of God; which order came, not by man, nor the will of man; neither by father nor mother; neither by beginning of days nor end of years; but of God;

29 And it was delivered unto men by the calling of his own voice, according to his own will, unto as many as believed on his name.

30 For God having sworn unto Enoch and unto his seed with an oath by himself; that every one being ordained after this order and calling should have power, by faith, to break mountains, to divide the seas, to dry up waters, to turn them out of their course;

31 To put at defiance the armies of nations, to divide the earth, to break every band, to stand in the presence of God; to do all things according to his will, according to his command, subdue principalities and powers; and this by the will of the Son of God which was from before the foundation of the world.

Josh Chandler explains how to enter the rest of the Lord through faith in Jesus Christ.