An "Alien" deck is made up of many Monsters, Spells and Trap cards that utilize a swarming strategy and explioting the use of "A-counters", which are used to weaken and sometimes take control of opponent's monsters. The aliens are on their own are relatively weak, the most attack points coming in form of "Cosmic Horror Gangi'el" and "Cosmic Fortress Gol'gar" with 2600. However, whenyou add in the effects of the a monster with the basic "Alien" effect (If a monster with an A-counter battles an 'Alien' monster it loses 300 attack and defence points during damage calculation only) it allows your smaller monsters to be able to take down opposing main threat monsters with relative ease. One of the main problems with "Alien" monsters is their reliance on "A-counters"; if your opponent has some way of negating the effects of your "A-counters" you lose your main form of offense. Thankfully, "A-counters" are very tricky to get rid off, since they aren't cards so you can not remove them by means of removal. The only way to remove "A-counters" is to destroy the card that they are put onto (excluding "A-Cell Incubator") or by using a card effect.
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