Question about armor slot

[Finaldeath]

What type of equipment goes in the bottom left slot? (round, looks like a shield would go there but doesn't)

I just took the boat from Athens Dock and still haven't found anything to fill the slot. I have looked at the wiki but it appears it only lists item types from standard titan quest and not the expansion (which im guessing this slot came from)and the picture shown of the inventory doesn't have the slot.

[thorvaaldr]

It's for Artifacts, which are thingies you craft using recipes called Arcane Formulas. You find the Arcane Formulas as loot, or buy them from vendors, then you hunt down all the ingredients (demon ichor, Essence of Achilles, etc) and when you collect them all, you take them to an Enchanter (a type of merchant) and pay him to turn them into an Artifact.

I think the lowest level Artifacts I've seen kick in around level 14 or 15.