"Ally of Justice" (Ａ・Ｏ・Ｊ（アーリー・オブ・ジャスティス） Ārī obu Jasutisu) is an archetype of DARK Machine monsters used by the Ghost army, Diablo in Yu-Gi-Oh! 5D's. They are empowered during the user's Battle Phase when the opponent controls LIGHT monsters. The trump card of the archetype is "Ally of Justice Catastor", who destroys any non-DARK monster in battle. The "Allies of Justice" are introduced in Duel Terminal - Synchro Awakening!! with further support in Duel Terminal - Invasion of Worms!!, Duel Terminal - Justice Strikes Back!! and Duel Terminal - Dragunity of the Hurricane!!. TCG-wise, they have been released in Hidden Arsenal.