Aughild's Treasured is one of the 2 craftable sets that use Nightmare materials (Shimmering Essence & Lizard Eye); with the other one being Captain Crimson's Attire. Interestingly, these sets do not have any overlapping parts and neither of them has a weapon (which is usually low dps in sets, cf. Hallowed Armaments) - so it is possible for a character to wear both at the same time.
All set plans, including this one, will teach your blacksmith to craft each piece in the set permanently. To learn this plan he needs to be level 6 (Illustrious).
The only recipes that need Fiery Brimstone for crafting; are the level 60 set and legendary items. Note that this also means the level 60 rare plans (e.g. Exalted Grand Vambraces) don't need brimstone, making them a much cheaper alternative in some cases.