Iratu's Harness is a leather cross-belt worn by Iratu. It appears to be be based on the leather shoulder sash he received from his foster father, Darius Elexion. Darius gave Iratu his sash when he gave him his Moon Emblem. At some point, Iratu modified seems to have modified it with a second strap turning it into a cross-belt harness whilst he was in Hell.
The cross-belt holds his Moon Emblem on a clasp in the center of his chest.
Later on, Tsavo adjusted the clasp so that Iratu could turn his Moon Emblem upside-down and render its power temporarily inactive. This shrinks him to his normal [relatively small size] which allows him to enter buildings he wouldn't otherwise be able to in his larger state. He originally needed to detach it entirely which put it at risk of being lost or stolen.