If you researched other religions, Christianity is the mix of all of them but under one God and belief of evil and the followers are slaves of rules that determines what happen after their death. In Asatru, the religion thousands of years before Christianity and possibly before Muslim and Judaism has a Goddess named Hella which was banned from Asgard and was sent to rule the underworld named Hel, and there are demon like creatures in her realm plus in that religion there are different realms of different races of creatures which could have even more demons. In the end days or the apocalypse or in Asatru; Ragnorak, the gods will face this huge wolf which is described having demon like powers. So demons could exist and haunt the living or Christianity has lots of good actors. Plus one of the gods in Asatru is named Loki, a trickster which can take form of a human to mask his true appearance like the other gods and create some sort of "prank" on the Christians. I believe that whatever religion you believe in that has some type of powerful being or beings will judge you by what happened in your life and how you died then decide whether to let you enter their home to you which for me is Valhalla. I am an Asatruer and I have converted to this religion after years of being a very religious person in the Christian faith. I've been through shit in my life and prayed to that God yet no answer until I started to pray to the Nordic Gods which answered back in some way. Call it bullshit if you want but with religion itself is all about experience of some type of magical situation that happen to you, to make you a true believer of that faith.