If they’re already saviours, how is anything much of a test or challenge? Heroes need to struggle or the battle is meaningless. It has to be possible for them to lose, yet find a way to win. And are they the ones who killed the sibling? Doesn’t sound very saviour-like. If it wasn’t them, who was it? Why are they not part of this story? Or are they part of this story and it just hasn’t been mentioned here? Sometimes too much information creates questions based on a need for comprehension rather than interest.

Too many commas. Make it simple and straightforward: protagonist, antagonist, conflict, stakes. Don’t weigh it down with unnecessary details or descriptions, like the bad guys being strange or 1200 years old or hatched from eggs. Nobody needs to know that yet. Just provide the basics. One adjective usually works.

“Five super-powered Earthlings must save the galaxy from ancient celestial warriors out for revenge.”

Maybe a little too short and not enough detail, but the four basic needs are there, and it encourages people to read more — like a summary or synopsis or even the script — to find out what happens and why. It makes people want to know: what powers do the humans have? What are these celestial beings like, how do they fight? Revenge for what? It doesn’t say, but it’s intriguing without being unclear.