Every Tailoring Recipe Required To Reach 350
As with many of the zones added in Planes of Power, PoNightmare has its own set of Tradeskill items and recipes that you'll have to farm and create in order to raise your Smithing from 300 - 350. Along with the Smithing recipes there's also a few Jewelcrafting recipes, Brewing Recipes and even a Baking Recipe or two that you can learn from the materials these enemies drop.
The items that we're going to want to keep an eye out for while farming the Hobgoblins are as follows...
Hobgoblin Meat (Baking Recipe)
Brick of Nightmare Iron (Smithing Recipes)
Midnight Stone (Multiple Recipes; involved in a lot of subcombines and arguably the hardest part to farm)
Nightmare Mephit Skin (Tailoring Recipes)
Nightmare Mephit Blood (Brewing Subcombines)