Chapter 46: Louise's killing intent
"The Spirit Realm is a world no human or race can enter. It has its own rules and existences. For example, if you make contact with people from there, you'll be able to make a contract with them. Some spirit races gladly leave their realm to cause chaos in our world, so their contracts are simple. Some contracts just allow people to summon them in a battle, and more."
"That's interesting." Leon nodded, knowing that information from Celes already. But it was good to learn about it from a different perspective, so he genuinely thanked the man for his wisdom.
And the talk carried on. "They can't die in our world. If they suffer a death blow, they go back to their realm for resurrection. But that doesn't happen in lands that split from The Spirit Realm. That land becomes abandoned, the spirit monsters lose their immunity, and we can contract them for life."