The Spirit
The Spirit... - testifies and teaches of the truth of all things ( Moroni 10:5 ) - shows us all things what we should do ( 2 Nephi 32:5 ) - comforts and teaches and reminds us of what Christ has said ( John 14:26 ) - enlightens the mind ( Doctrine and Covenants 6:15 ) - speaks peace to our souls ( Doctrine and Covenants 6:23 )