[brxbrx]

Blood hunting is an involved process, looking for young virgin girls of an unspecified genotype hidden amongst thousands of people and dispersed throughout an entire process. It's not something you can do in secret.

To patrol, use cavalry, or create those statue thingies that shoot lightning out of their eyes. You're Vanheim, you should have earth/air available.

Your population will shrink faster when you combine blood hunting and patrolling, but a province of 10k should still last you a few years before you should move on. Blood hunting in your capital is generally risky, since that's always an important income and production center.

Order and growth domains would help curb the population loss, but I don't need to tell you that (personally, as someone who enjoys being thematic and even rping. I've a hard time imagining a blood nation with both growth and order. Maybe Mictlan).