No, the daemons are just part of the environment. They live in dark places and come out at night.

We were at war with an empire called Niflheim. They had more resources and better technology, so they'd already taken over the rest of the country. But there was a barrier over the city that kept both daemons and Niflheim out, and they couldn't breach it, so the war reached a stalemate.

Eventually our countries agreed to sign a peace treaty... but ... I guess... Niflheim used it as a pretext so they get into the city and destroy the barrier from the inside.