Someone needs to open the door for them. Via sacred geometry. It's like magical math that I guess is supposed to contain the back door that Lucifer built into heaven, but also has to do with Sumerian things. But terrible people do what's called "opening the door" for the children. And they all have something in common, but we're not sure what exactly it is now. There's a genetic component, I think, and also the kids who have the doors open for them often are given, or exhibit powers. We don't know what comes first, the door or the ability to summon them. It's kinda chicken and egg.