[What will you do, Nikolai?]
After his conversation with the previous patriarch, Alucard, Nikolai left Nikita and Selene. He told them there was something he needed to take care of.
Thankfully, they believed his words and let him leave without issue.
'What am I supposed to do, those people can't be trusted.'
[I know, but that's not the only thought you have, right?]
Elizabeth knew that her son's goal was to bring her back. However, she also believed his plan wasn't just to give her any old body.
He studied the spirit engineering book and borrowed several alchemy books from the auction house in the Arena. When he wasn't training or flirting with the three girls, Nikolai spent his time studying and improving his usage of Soul Force.
There wasn't much else he could do right now because he lacked clues.
'Mother...'