They were introduced in Ancient Sanctuary, and were reprinted in Dark Revelation Volume 2. They made a return in the Lost Sanctuary Structure Deck/Structure Deck: Lost Sanctuary. After many years of inactivity, Duelist Alliance revitalized the archetype once again with the introduction of their only DARK monster.
"The Agent of Judgment - Saturn" appears as a character in Yu-Gi-Oh! World Championship 2007, "The Agent of Mystery - Earth" appears in Yu-Gi-Oh! Duel Arena, and "Master Hyperion" appears in Yu-Gi-Oh! 5D's World Championship 2011: Over the Nexus.
The first "The Agent" monsters to be released focus on Life Points: "The Agent of Force - Mars" gains ATK when its controller's Life Points are higher than their opponent's, and "The Agent of Judgment - Saturn" can inflict damage to opponent equal to the difference in the players' Life Points.
"The Agent of Miracles - Jupiter" can banish any "The Agent" monster in the Graveyard to increase a LIGHT Fairy monster's ATK by 800. Also, when "The Sanctuary in the Sky" is on the field, Jupiter allows the player Special Summon 1 banished LIGHT Fairy monster by discarding a Fairy monster.
More importantly, "Master Hyperion" can be Special Summoned by banishing an "The Agent" from your hand, field or Graveyard. Also, by banishing another LIGHT Fairy monster, you can select and destroy any card on the field. If you have "The Sanctuary in the Sky" on the field the player may use this effect twice per turn.
Strategies and tips
A common strategy is to use "The Agent of Creation - Venus" to Special Summon 1-3 "Mystical Shine Balls" by paying 500-1500 Life Points in order to set up the Graveyard for either the Summon of an "Archlord Kristya" or "Master Hyperion" as soon as the very next turn. "The Agent" Decks can also Summon strong monsters from the Extra Deck. If the opponent tries to avoid such a fate by not attacking the "Mystical Shine Balls", then they still run the risk of a Summoned "Earth" being Tuned into a Level 4, 5, 6, 7, 8, 9, or 11 Synchro Monster, in addition to the Fairy player gaining a free card with the effect of "Earth". The Summoned "Mystical Shine Balls" can also be used to summon Rank 2 Xyz Monsters. "Earth", can search for any "The Agent" or "Master Hyperion" (provided "The Sanctuary in the Sky" is on the field) when it is Normal Summoned. "Genex Ally Birdman" can also be used for Synchro Summoning or Xyz Summoning a Rank 3 monster. "Hyperion" can also be used alongside "Earth" for Level 10 Synchro Summons, such as "Leo, the Keeper of the Sacred Tree". If there are two copies of "Hyperion", they can even be used for Rank 8 Xyz Summons, such as "Number 107: Galaxy-Eyes Tachyon Dragon", which can be deadly when used in conjunction with "Hyperion" and "Honest".
Despite the enormous potential and consistency that "The Agent" Decks can have, they are not without their weaknesses. "Archlord Kristya", a oft-played trump card in "The Agent" Decks themselves, can be as strong of a foe as it is an ally. Kristya's effect prevents a "The Agent" Duelist from Summoning "Master Hyperion" and "Black Luster Soldier - Envoy of the Beginning", key cards to maintaining a foothold in the game. Due to the LIGHT monster emphasis, "Light-Imprisoning Mirror". Most of the competitive "The Agent" Decks are also hybrids (e.g. Chaos, "T.G.", and Tele-Agents), making "Gozen Match" another potential threat.
"Gravekeepers" also pose a distinct threat with "Necrovalley". Its effect of sealing the graveyard locks down most of the power plays a "The Agent" Deck may have. "Skill Drain", "Effect Veiler" and the opposing "Herald of Orange Light" are also grave issues, as the combos in most "The Agent" Decks are highly reliant on monster effects.
Perhaps the most effective cards to play against "The Agent" cards are "Dimensional Fissure" and "Macro Cosmos", because they instantly close any Graveyard access for storing resources. They also render "Effect Veiler" and "Herald of Orange Light" useless, as their activation costs cannot be paid. For this reason, one should consider having in the Side Deck, if not the Main Deck, multiple copies of "Mystical Space Typhoon", "Twister", and "Dust Tornado".
- Tori Meadows often uses "The Agent" monsters in video games, despite not using them in the Yu-Gi-Oh! ZEXAL anime or manga. This is a reference to her Japanese voice actress Mikako Komatsu using a "The Agent" Deck in Yu-Gi-Oh! Official Card Game tournaments involving Yu-Gi-Oh! voice actors.