As soon as the two girls accepted the proposal, for reasons only they knew of, Klaus started preparing for the night.
He bought some fragrant flowers and herbs, especially ones that let go of all inhibitions. He placed the herbs and let the smell spread across the room. He plucked the petals of the flowers and tossed them on the bed.
Just as the preparations were completed, Callie arrived at his dorm late in the night, making sure no one knew about this. He quickly led her to his room, while Liliana was instructed to enter in the later part.
Since Callie is considered the outsider, he wanted to make sure she was comfortable. He also wanted her to stay and run away after seeing two people naked and having sex. If they are the ones who are doing it, then there is a chance that she won't leave even when Liliana makes her appearance.