The Ring of the Giant's Layer

It's a plain sort of bronze or maybe even copper ring. It doesn't have any sort of etching or anything on it. You wear it and it grants you some extra proficiency when battling something much larger than yourself. While you're wearing the ring, you have plus one attack against. And plus one AC versus attacks done by enemies who are of the size category large - which means 8 to 16 feet or higher.