The Onyx Shield is shaped like a large, square diamond with silver edges. The face of the shield is black with thin, violet edges on the top and bottom corners. A circular, silver bolt or pin is present on each of the two side corners on the shield. The shield's face is also adorned by four large, yellow, interweaving rings. The top and bottom rings each have a rectangular protrusion on them. It is a palette swap of the Mythril Shield.
Onyx is a color of pitch, shiny black.