"Watchghoul" are Dark/Zombie-Type based archtype. It focuses on multiple summons, fast synchro summons, keeping a bunch of cards at hand and at field during the End Phase for counters and comebacks, and it weakens by time the opponent's streagth. The main purpose of the archtype is to summon the powerful "Watchghoul" synchro monsters, with effects which allow you to take control of monsters, steal cards from your opponent's hand, watch the hand and the face-down cards of your opponent, negate effects, prevent your opponent from activating card effects during the battle phase and drain the opponent monsters' streagth for LP. They must also be supported by the "watchghoul" S/T cards. "Watchghouls" can be powerful, but they can be countered, but if they are used wisely, and are supported by other zombie-related cards - in other words if you add them in your zombie decks - they can be decent.
Next: "Acidust"