JKSManga
So Hilston is trying to find someone stronger then him most likely his goal is to take Sil's body. It has been mentioned he is quite old we know his father who met someone with abilities they couldn't copy and it was record down that a Blade met a shadow user before. Considering the vampires left Earth quite long ago these events would have happened years ago. Most likely Hilston has been switching bodies hence why he makes children with his DNA and runs the Blade family like he does in order to make someone that would hopefully be able to have all abilities one day.