slayer vs. demons plot

In the hot, crisp Sahara desert, archeologists found an ancient temple deep under the mounds of sand while heading towards another African state at night. It seems only a small part of it was revealed but they were curious so they continued the dig. However, they found a temple that seemed to have different structures of Roman, African, Egyptian, and Aztec influence. But they didn't understand why unknown symbols were put on the walls and pictures of angels and devils. Inside, they accidentely opened a portal meant to be closed for centuries... and demons slaughtered everyone in sight. But something was different, since usually they take form of shadows. But now, it seems they can take human form in order to invade into the human world. Humans have started to see strange cases with these creatures and barely know anything about them but few decided to set up a slayer society in order to protect humankind from these gruesome creatures. The thing is... they don't know a lot about them.