Orgnum's Scales is one of the craftable sets providing special bonuses to armor and weapons. It is available for crafting to players pursuing blacksmithing, clothing and/or woodworking professions. The special crafting site dedicated to creation of this set is available in the Earth Forge on completion of the Fighters Guild quest line.
The Prismatic weapon chosen by the player on completion of the Fighters Guild quest line will automatically be a part of the Orgnum's Scales set.
Since the Earth Forge is not associated with any of the Alliances, there is only one crafting site for this set.