The phrase "to save the galaxy" means to rescue and protect the entire galaxy from danger or destruction.
Sentences with «to save the galaxy»
Her only problem, besides saving the galaxy, comes from the man she must work with. (deanwesleysmith.com)
Will she be able to save the galaxy while everyone is out for her blood? (retronuke.com)
If you're looking to get up to speed before saving the galaxy from ancient alien threats (as usual), here's everything you need to know about Halo 5: Guardians. (tomsguide.com)