After an explosion opens a hole for demons to escape from Hell, the dweller of humanity, aka the devil’s son, goes to earth to run up the demons before Yahweh sends his armies to clean up the mess, sending every demons into oblivion along with the dweller, if he’s still there.

There are some questions that spawn from reading this logline. What explosion is this? Who caused it? Was it accidental? If so then you don’t need to say that an explosion opened the portal, you can just say that the portal was opened. Also as Richiev said, it works so much better with a ticking clock. That way we feel the urgency and stakes.