There is nothing more powerful than the ability to control the dreams of humans because this can have an incredible impact on their decision making. The manipulation of dreams is one of the most popular methods that the order use to control humans. This has led to may critical decisions that human leaders have made in the last few centuries. The methods to control dreams are basically with the use of psychic forces that many order members possess.
The beauty of controlling human minds with this method is that it allows them to think that they are not being influenced at all. This is the perfect way to get them to do anything that the order wants without any suspicions been raised. The order has been challenged in the past by top ranked human leaders that have hired human psychics to protect them, but most of them never last long.