Iron Ring
As mundane as it possibly could be. The only useful thing it can do is to protect your finger from being cut off some day. Perhaps.
It can be created in a Crafting Table, via shaped recipe:
Alternatively, there is a small chance to find it in most of the Overworld dungeons.
When worn in the Ring slot, it will give the wearer +1 Armor Points.
This is a crafting component, used in recipes of all rings in the mod - even though it can offer a bit of usability on it's own.