Alien " Alien " ( Japanese : エーリアン " Ērian " ) is an archetype of Reptile monsters . They were introduced in " Power of the Duelist " , with further support added in " Cyberdark Impact " , " Strike of Neos " , " Force of the Breaker " , " Tactical Evolution " , " Gladiator ' s Assault " , " Crimson Crisis " and " Raging Battle " . " Alien " Decks focus heavily on exploiting A - Counter s , which weaken opposing monsters when they battle " Alien " monsters and facilitate the effects of " Alien " cards and related support . Design . Appearance . They seem to be based on many science - fiction views of aliens , and the way they operate in stories , making use of such tropes as brainwashing , genetic manipulation , and biological experimentation ( as evidenced by " Interplanetary Invader " A " " , which appears to be a mutated , living , or even intelligent form of an A - Counter ) . Their appearance seems to draw inspiration from these as well , like big eyes , tails instead of feet , large claws , long tentacles , slender bodies , multiple arms , etc . Some " Alien " monsters resemble the stereotypical s , while others are more reptilian in appearance . Etymology . The archetype ' s name comes from the term : " " , an extraterrestrial being from outer space . Playing style . " Aliens " have a variety of lower - Level monsters , such as " Alien Warrior " and " Alien Grey " , that generate those essential A - Counters . However , prior to " Crimson Crisis " , they suffered from a distinct lack of effects to exploit these counters once created . Cards like " Alien Telepath " , " Alien Hypno " , and " Alien Mars " have potentially disruptive , yet situational , effects . The powerful field - clearing effect of " Cosmic Fortress Gol ' gar " , as well as the revival engine provided by " Code A Ancient Ruins " , lends the Deck a more reliable means of converting A - Counters into Card Advantage . " Crimson Crisis " introduced " Planet Pollutant Virus " , a card which doubles as mass - removal and lingering A - Counter generation . Cards like " Alien Overlord " from " Crimson Crisis " and " Alien Dog " from the subsequent " Raging Battle " also gave " Aliens " a bit of swarm ing power . There are several different builds and play styles for the archetype . The " Alien " cards prior to " Crimson Crisis " emphasized lower - Level effect monsters like " Alien Psychic " and " Alien Hunter " , and monster manipulation in the form of " Brainwashing Beam " and " Mass Hypnosis " . A viable strategy , it is distinctly suboptimal when compared to modernized builds that emphasize " Gol ' gar " and the easy destruction and revival it supplies through its quick counter generation for " Code A Ancient Ruins " . " Gol ' gar " can further be paired with powerful Continuous Spell Card s like " Prohibition " or " Burden of the Mighty " , along with cards like " Ancient Forest " and " Swords of Revealing Light , " to create a strong control archetype that excels at A - Counter generation via the effect of " Gol ' gar " . No monster in the archetype has over 2600 ATK , a value shared by " Gol ' gar " and its underrated predecessor , " Cosmic Horror Gangi ' el " , together the so - called " boss monsters " of the " Aliens " . The Reptile " Evil Dragon Ananta " is often included as a third " boss monster " and can often turn the tide of a duel via its field clearing abilities . None of these monsters count as " Alien " monsters , per se , and hence do not weaken opposing monsters burdened with A - Counter s . This drawback is largely irrelevant , however , especially in the case of " Gol ' gar " , which is the highest ATK Level 5 Monster Card in the game and able to eliminate most threats from the field either by its effect or its disproportionately high ATK . All " Alien " Decks ultimately rely on A - Counters to operate . A swarming " Alien " Deck needs ample A - Counters to Special Summon " Overlord " and activate " Code A Ancient Ruins " . " Alien " Decks that manipulate the opponent ' s monsters via " Alien Hypno " , " Brainwashing Beam " , and " Mass Hypnosis " require A - Counters to maintain control of pilfered monsters . Another important effect of an " Alien " Deck is the A - Counter ' s ability to reduce the ATK and DEF of a monster by 300 points for every counter on it . The effect reduces the ATK of Monsters fighting " Aliens " for each " Alien " with that effect on the field . More easily explained , ( Number of monsters with ability ) X ( Number of counters on monster fighting an " Alien " ) X 300 = Amount of ATK lost . Most " Alien " monsters have this effect built in . Some " Aliens " with powerful effects , like " Alien Hypno " and " Alien Dog " , do not . Gol ' gar control variants obviously exploit the effect of " Gol ' gar " to both generate A - Counters and to instantly convert those counters into free removal . A popular combo involves " Cosmic Fortress Gol ' gar " and " Swords of Revealing Light " : By using the effect of " Gol ' gar " to return face up Spell and Trap cards of your choosing back to the owner ' s hand , you can return your " Swords of Revealing Light " back to your hand and play it back on the field . By repeating this you ' ll have unlimited " Swords of Revealing Light " . Also you ' ll put A - counters on all face up monsters on the field including your own , and destroy pesky cards that your opponent controls ( you can only use this combo once per - turn ) . Weaknesses . " Aliens " are weak against Decks with superior speed , such as " X - Saber " , " Legendary Six Samurai " or " Blackwing " . The Deck itself has little draw power outside of " Grey " , which causes it to have trouble against faster Decks . Specialized searcher s such as " Gold Sarcophagus " , " Oshaleon " , " Snake Whistle " , and " Damage = Reptile " can partially alleviate this problem by letting you retrieve your combo pieces more efficiently , but not all of them fit comfortably into the archetype and many of them can be situational as draws . You can also add " Pot of Duality " for more consistency to the deck . The deck is also weak against " Fire King " Decks , as Fire Kings rely upon the destruction of cards and Special Summoning from the Graveyard , as well as clearing the field of monsters and Spells , which can force Aliens to stall . It is difficult for Aliens to overcome a card with high ATK and no DEF . The " Alien " - based Deck is also bad against " Gladiator Beast " , as they constantly tag out , preventing A - Counters from piling up . In this matchup , Aliens have to rely on pure power , which is not generally their focus . You can put a " G . B . Hunter " in your Side Deck to counter this . " Aliens " aren ' t much use against " Ghostrick " Decks , as most " Ghostricks " have the ability to flip themselves facedown , clearing away any counters on them and preventing more from being added . Additionally , their low attack power means it will be difficult to do damage even while a " Ghostrick " Field Spell Card is active . " Aliens " also have no native , major offensive threat outside of " Gol ' gar " . Although " Warrior " and " Shocktrooper " boast high ATK for Level 4 Monster Cards , they quickly lose value after the few first turns of the game , when Fusion Monster s , Synchro Monster s , Xyz Monster s and other powerful cards begin hitting the field . Gol ' gar helps to keep " Aliens " in the race . Other Synchros , like " Ally of Justice Catastor " ( instantly Summonable by " Ammonite " and useful against " Lightsworns " in particular ) , also help the Deck to keep a solid footing against speedy Decks . " Counter Cleaner " and " Enervating Mist " can also seriously hamper " Alien " Decks if used correctly due to their high reliance on A - Counters .