Forgemaster
While other warriors wage battle with the inferior weapons they are able to purchase or find, you labor away at the forge, constantly improving your tools. After all, a fighter is only as strong and sharp as his blade, and yours is the sharpest of them all.
Bonus Proficiencies
When you choose this archetype at 3rd level, you gain proficiency with smith's tools, if you don't already have it. Your proficiency bonus is doubled for any ability check you make that uses your smith's tools proficiency.
Magic of the Forge
At 3rd level, you are able to imbue magic into a weapon or armor. At the end of a long rest, you can touch one nonmagical object that is a suit of armor or a simple or martial weapon. Until the end of your next long rest or until you die, the object becomes a magic item, granting a +1 bonus to AC if it's armor, or a +1 bonus to attack and damage rolls if it's a weapon.
Once you use this feature, you cannot use it again until you finish a long rest.
Superior Craftsmanship
At 7th level, you are able to craft equipment superior to that of other tradesmen. By spending an hour at the forge, you are able to craft a nonmagical item that must include some metal: a simple or martial weapon, a suit of armor, ten pieces of ammunition, a set of tools, or another metal object (see chapter 5, "Equipment," in the Player's Handbook for examples of these items). The creation is completed at the end of the hour.
As a part of crafting this item, you must use raw or smelted ores worth the value equal to the creation you are making.
When your crafting is completed, the item gains the masterwork property. Masterwork armors reduce their strength requirements by 2, and weigh 3/4ths as much as a normal suit of armor. Masterwork weapons deal an extra 1 point of damage on a hit. Masterwork tools grant a +1 bonus to ability checks made with that tool.
Innured to the Flames
Starting at 10th level, your mastery of the forge grants you resistance to fire damage. Additionally, when you use your second wind feature, you gain a number of temporary hit points equal to the amount you heal.
Pristine Craftsmanship
At 15th level, items you craft become pristine. A pristine object does not suffer from corrosion by acid or other means, like from the black pudding's corrosive form feature. Furthermore, pristine items count as magical for the purpose of overcoming damage resistance.
Champion of the Forge
At 17th level, your dedication to the forge manifests in your blood. You gain immunity to fire damage, and while wearing heavy armor, you have resistance to bludgeoning, piercing, and slashing damage from nonmagical attacks.