Fighter/2nd/Darknut

Mettle

Starting from 2nd level, all Heart Containers you gain from this class become d12s instead of d10s—including the one you gained at 1st level.

Your heart point maximum increases by 3, and it increases by an additional 1 every time you gain a fighter level after this.

Armor Expertise

A darknut is often defined by the ability to forge and improve its own armor. Starting from 2nd level, you have proficiency with smith's tools, and are an expert on any ability check made with them to create, modify, or repair armor. If you are already proficient with these tools, you can either gain 1 proficiency point or become proficient in any other artisan's tool of your choice.

Stalwart Defense

At 3rd level, you gain the Armored Defense and Knuckle Defense fighting styles. If you already have either fighting style, in its place you gain an additional fighting style of your choice.

If you are wearing medium armor, you can add your Constitution modifier to your AC in place of your Dexterity modifier.