The term 'highest-order angel' refers to a SERAPH, which is a six-letter word. A SERAPH is an angel of the highest order in the hierarchy of angels. They are often depicted as having six wings and four faces, representing the four cardinal directions. In Christianity, they are seen as the guardians of God's throne and the protectors of Heaven. In Judaism, they are seen as the guardians of the Tree of Life. In Islam, they are seen as the guardians of the Kaaba.