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 "Worms", 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.
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".
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 effects while the "Cybers" are high-level machine LIGHT monsters that can not only attack multiple times, but can swarm the field.
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.
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.
"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.