Vanilla Harpie decks uses normal Harpies, and Mai's exclusive skill Harpies' Hunting Ground. The combination of Order to Charge, and the ability to destroy your opponent's backrow, makes it quite versatile, which can then be often updated with newer cards from new boxes.
Generally, the way you play Harpie decks is to simply summon the Harpies to destroy your opponent's backrow before attacking their monsters. This will allow you to attack your opponent's monster without having to worry about their spell/trap cards. If your opponent summons a stronger monster with a higher attack, then you use Order to Charge to take them down.
Harpies' Hunting Ground is what makes Harpie decks quite strong, but it can potentially be a weakness as well. Since Harpie decks are quite common, people have been bringing cards to counter this field spell. If your opponent has no spell/trap card, summoning a Harpie monster will activate its ability, forcing you to choose your own card. Cards like Security Orb, and Wild Tornado are also getting more common, making you think twice instead of blindly choosing to destroy your opponent's spell/trap card(s).
The non-effect Harpie monsters are often used because of Order to Charge, which is a really good card that allows you to confidently summon this card, despite its low attack. It can be used to destroy most monster your opponent summons, and can be activated during their turn. But you can use the other different Harpie monsters, which offers different effects and can be useful depending on your playstyle.
The effect of Harpies' Hunting Ground is activated even when your Harpie monsters are special summoned from the graveyard.
Since you can only put 3 Harpie monsters, you will need to use other monsters in the deck. If you want to use Order to Charge, it's better to put normal monsters like Sonic Duck, or Blazing Inpachi since they have high attack. They both have low defense, but it won't matter that much if you have an Order to Charge at the ready.
Harpie Lady Sisters
|Put 1 copy of this card if you feel like the deck is running slow.|
|Surviving for a turn is not difficult because of the spell/trap cards in the deck, making it easier to summon this.|
|2 or 3 copies of this card with 1 Harpie Lady Sisters to increase the chance of getting it.|
Big Bang Shot
|Useful when you equip it to your monsters or banish your opponent's monster when you destroy it with a harpie.|
Adhesion Trap Hole
|Weakens your opponent's monster to ensure that you can destroy it with any monster.|
|Can be used to destroy any face up card when you have a harpie card with the hunting ground still active.|
|If your field spell gets destroyed, you can return it to your hand using this card.|
Symbols of Duty
|Can be used to special summon any monster from your graveyard, or your opponent's graveyard.|
Harpie Lady 1
|Increases your other monsters' attacks.|