Draculus's understanding of the Multiverse is not that deep yet.
Therefore, he doesn't know much about such peculiar situations as the Son of Fortune.
It was only when he went to those worlds to look for some people who shouldn't be alive that he read some of their books and learned a bit about the related knowledge.
After all, it is already an open Devil World, and it suffers from endless attacks by demons from the Void, so the devils treat those who sincerely submit to them quite well.
The necessary knowledge is all given.
There are a few guys who gave up their humanity quite early, and Draculus indeed had to spend some effort when dealing with them!
He can't just kill his own people and ignore the outsiders, right?
Although these guys do not pose much of a harm to those students of Draculus who went out later, in the very beginning, they cooperated with the devils to either kill or capture the first few batches of his disciples who left.
