Ally of Justice " Ally of Justice " ( " 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 " . Duel Terminal story . On this distant star , each tribe or clan fights to ultimately reign supreme . For the longest time , the war just waged on , with no one group holding the advantage . However , this battle that no one thought would ever end was suddenly brought to an abrupt halt , as the " Worm s " , invaders from outer space , suddenly crashed on the planet . To combat the invaders , the tribes and clans were forced to form a truce and unite together . The four tribes that were the most powerful forces on the continent form their own organization , " Ally of Justice " . Bringing together each of their technologies and crafts , they began to develop anti - Worm weapons . Playing style . This archetype is rather unique among all others . Most archetypes tend to not focus exclusively upon destroying one particular category of opposing monsters . Indeed , against most Decks many of the cards in this Archetype will be useless . Fortunately , " DNA Transplant " can be used to set all opposing monsters to LIGHT to benefit from their effects while protecting it with " Imperial Custom " . If using " DNA Transplant " , " Lyna the Light Charmer " can help you take over your opponent ' s monsters ( if the Attribute ' LIGHT ' is selected with " DNA Transplant " ) . Also , since all monsters on your field are LIGHT , you can use them to Synchro Summon " Light End Dragon " to your side of the field . When " DNA Transplant " isn ' t on the field all your " Ally of Justice " monsters will be DARK and as a result you can Synchro Summon " Dark End Dragon " to your side of the field . " Allure of Darkness " is also handy in this Deck even with " DNA Transplant " on the field because Ally of Justice monsters are still DARK - Attribute when in your hand . " Allies of Justice " are designed to counter the " Worm " & " Cyber Dragon " archetypes ( specifically the LIGHT Reptile series ) , as the " Worms " are LIGHT monsters with Flip effect s while the " Cybers " are high - level machine LIGHT monsters that can not only attack multiple times , but can swarm the field . Decks . Swap Justice . Instead of relying on your opponent playing LIGHT monsters . Instead use cards like " Creature Swap " or " Mystic Box " to give control to your opponent a LIGHT monster you control instead . So you can give your opponent a Gold or Silver Gadget and then Summon another Gadget from your deck . Weakness . Although " Ally of Justice " are strong when battling LIGHT monsters they can be countered with cards like " Skill Drain " , " Destiny HERO - Plasma " and " Angel O7 " ( even though " Angel O7 " is a LIGHT monster he negates any effects on the field ) . To counter those cards use cards like " Royal Decree " and " Lightning Vortex " . " Acid Rain " , " Magnetic Mosquito " and " System Down " also hurt the deck because they clear the field of all Machine monsters on the field ( especially " System Down " because it banish es them ) . Unfortunately , the vast majority of your monsters have no other positive effects when facing a deck that isn ' t primarily LIGHT . Even with " DNA Transplant " most of your monsters will still struggle to overcome any monster with very high attack or multiple monsters at a time . Even when facing a LIGHT deck , it is very easy for your deck to get outpaced or overwhelmed without your having disruption . Competitive History . " Ally of Justice " as a Deck on its own has never seen any large scale success . However a handful of their monsters have seen competitive play during formats that had large amounts of LIGHT monsters . " Ally of Justice Catastor " saw years of competitive and casual play as a fantastic Synchro option from mainly 2009 to 2013 . " Catastor " could deal with many boss monsters for the time , as well as being extremely easy to Summon as a generic Synchro Monster . Even now it is a fantastic option against many monsters in the game . " Ally of Justice Cycle Reader " has also had major success against " Lightsworn " and " Blue - Eyes " Decks , and is also useful due to being a Tuner monster .