It sets up a specific set of rules and then actually sticks to them
It can be a little irksome when a film - even one as ultimately silly as "Demon Knight" - sets up the rules of the world and then defies them at every turn. Dickerson doesn't fall into that trap. Witness the consistency of the "blood seal" rule, which doesn't allow the Collector or his minions to pass through any entrance sealed off with the fluid contained in Brayker's key. It may seem like a small thing, but it's shockingly rare for a genre film to abide by its own conventions.