Soul Binding. Although it was actually a simple procedure of binding one's soul with something—usually a High Grade Artefact or Relic—in Asia's perspective, Basil was devouring her.
Technically, Basil wasn't even binding his soul with Asia; he was merely reattaching a soul that had been split in two in the past. Of course, the result was the same as if he was binding his soul to her, since "Vagus" was already bound to him.
Asia, who had wanted to keep everything to herself, was extremely dissatisfied this happened to her. She had planned to self-destruct after Basil left the space to keep all the things he would eventually figure out in the future.
Alas, Basil had perfectly seen through her intention, so her plan to self-destruct was nothing but a mere plan. She, of course, didn't just let him do what he was doing as she tried her best to break the procession.
