The Melchizedek priest is the creator. The Greek, both here and in Psalm 102, says not "in the beginning" but "according to dominions," showing again that the Melchizedek priest always acts by power, authority, and dominion (the Hebrew doesn't have this phrase at all).
Psalm 102, by the way, is a "prayer for the ptochos." The ptochoi are the "poor in spirit" of Matthew 5.
The garments of the Melchizedek priest are eternal. The garments of others are mortal, and will pass away.