Several innocious questions, @Kingfisher
1) Is Demonblood literally just blood of demons?
2) Do vampires posess a classical weakness to being stabbed through the heart with a wooden stake?
3) In the ingame universe, is there sound information about origins of all the creatures that we'd consider "supernatural"? Are various species, powerful magics and the realms of fey, undead and demons completely mundane parts of the universe that can be explained through science and logic or are they something that is alien but exists nevertheless due to some other reasons?
1) Demons blood is a mixture of crappy street-level chemicals, with just a tiny hint of actual demon's blood. If you ingested an entire syringe of the genuine article you'd become a Fiendling.
2) Yep! Turns them into a pile of ash.
3) In this universe magic would be consider a school of science currently beyond comprehension. If you try to explain it you'd quite literally use your mind, so folks are just kind've forced to accept that some things are the way they are.
Hope that helps!