Supernatural
The Nasmaranian is an ancient evil (demon) that destroys families and communities. It’s been contained for centuries through a binding ritual to a human body.
The entity itself is unseen, though we see some kind of liquid (?) that transfers between people. It’s interesting that this movie is called The Mummy because no one is really a mummy. The monster is a demon who possesses humans, alive or dead. It also doesn’t seem to be a single entity, since it can transfer part of itself to others and exist in multitude. And when transferred, all of the variations are fused back into the one.
Its only weakness seems to be the ancient script covering the body in which it’s bound.