When an archaeologist dies by a powerful being, a package is sent to his girlfriend, containing powerful information leading to the destruction. The girl must find the items in the book in order to save humanity for the monster that is coming.

It sounds as if the girl is the MC, you need to describe her better than “…girl…” – that means nothing in a logline.

What is her major flaw? And, for god sake, please don’t make it ‘naive’… or ‘introvert’… these have become cliche go-to flaws and really come across as reluctance on behalf of the writer to give a female character a genuine flaw – give her depth and make her interesting.

Secondly, best you describe the events from her point of view, for example: After her fiance dies, while on an archeology expedition, a [good description] [main character] must…