None. They pick and choose. Or rather, I suspect Aurora's creator does. [He waves a hand and takes the staircase down to the first floor. Outside the sun is shining and weird giant birds wander about. Gift boxes are littered around like someone tossed them out of a speeding car.

Kaeya takes a look outside, shakes his head, and heads for the door.] For all we know, it could be that who gets picked is random.