A chosen earth gatekeeper must stay alive for 3 hours while the worlds mate,the mate open the gates to both worlds ,aliens seize the opportunity to invade earth,his death keeps the gate open forever and it means death for all mankind.

"When a portal is opened between our world and the world of a dark alien race, a gatekeeper has three hours to destroy the alien army and seal the gate for another thousand years."

Alas, the logline is:

1] Too long (41 words).
2] Too complicated to understand the plot in one quick read (which is how loglines are read).
3] A logline should only raise one question in the mind of a reader: "Will the protagonist achieve his objective goal?"

But this logline raises numerous questions, like:? What does it mean that worlds mate?? How do they mate?? ?What worlds are there beside the world we live on?? Open gates to both worlds?? What gates?? How will his death keep the gates open forever and doom mankind?

fwiw

After an alien gateway opens, the chosen gatekeeper must survive three hours until the eclipse to close the gates and prevent a full scale invasion (25W)

he is "the chosen one"..........to survive?! and if his death means the end, why didn't they choose someone better?