Humans and monsters were quite similar when it came to defending territory or protecting something important and meaningful, whether it was friends, family, or something material like money, resources, and things of value.
Sure, humans didn't occupy some territories without allowing others to enter them, but... technically, that's what they did, using money to buy various properties. The method changed as society reached the stage of advanced technology and bureaucracy, but the goal was the same.
If a person found something of value, they wanted to keep it or use it for their own good. Sure, each person had a limit to how far they could go for it, just like monsters.
If an artifact appeared somewhere in the Dead Lands, many people wanted to take it, from Phantoms to weak and strong monsters.
