The Eternal Forgemaster is an armor crafter in the Fissure of Woe. He can be found inside the Temple of War, but getting to him and having him ready to make armor will take a lot of work. He is the only one who can craft Obsidian armor. To get the Forgemaster to craft armor, you must first complete the quest The Eternal Forgemaster, then complete the two Temple of War quests listed below.
You can sell loot to the Forgemaster after finishing the quests, which is useful, since trips to the Fissure can take a long time to complete and may yield a lot of profitable items, often maxing players' backpack capacities.