Unstable Powerful Steelforged Essence

Unstable Powerful Steelforged Essence are what remains of Powerful Steelforged Essences, which can no longer be crafted. Prior to Shadowlands, using this item "restored" it into a Steelforged Essence and 25 Sorcerous Air.

Source
The original version of this item, Powerful Steelforged Essence, was crafted by blacksmiths with a skill level of 1. The recipe was learned from Recipe: Powerful Steelforged Essence, which could be purchased from The Forge at Lunarfall or Frostwall, or from the blacksmithing vendor in Stormshield or Warspear.