maybe I am missing something about the vampire castle and orb, but I thought the tower just had the castle and orb as an item to put in and he put it on a floor around the same time he put the tree on another floor. then one of his 2 beginning followers summoned, with magic, the vampire lady to take care of the castle but it wasn't like she was meant for the castle just that it would be a good fit like the high elf and the tree and she then summoned more vamps herself. however with what we learned from the chapter the castle, the orb, and the head vampire lady which was summoned later can't exist without each other. which doesn't add up to me cause they didnt bring in vampires from the outside who possibly lost their pervious castle and needed a new place to thrive like the other groups and gave them the castle they were all summoned so the story just seems oddly changed here. like the world tree thing there was a world tree outside the tower which got replaced or is getting replaced by the one he put in the tower, but nothing is talked about the castle outside or maybe i forgot about it. this would mean though that there should be another castle outside with an orb and a different head vamp.
or maybe im digging to much into this tower booba manga and should just enjoy the ride