My Godly Vampire System

*What if I make you to be a Vampire and give you a gothic-style castle, Are you interested? 
Not interested? Ok.. 
Then how about above all this I will also give a Godly system?! 
As an 24 years old Nerd, a Pessimistic Person, he had traveled to into this Fantasy Medieval Ages for a Week.   
Even if he encountered a major life event like transmigration, he still felt that it was normal. 
Although there were all kinds of magical creatures in this world.  Such as the Demons, unicorns, dragons and slimes..
He thought transmigration was just changing places to be a salted fish. 
When he got used to the life here, wouldn't he just live a mediocre life? 
Until one day, he came to the Annie Castle and turned into a Vampire…. 
"System has come online. Master has officially come into contact with the 'core building'. Newbie mission is now issued..." 
Now with the godly Vampire System, what is he going to do in this dark fantasy age?