The Stars Are Ours: Part 1 - Emergence (The Celestriad Book 3‪)‬

A military empire, an amnesiac stranger and a superweapon bequeathed to Celestra by its dying First Scientist. Three elements which portend disaster.
To preserve their future, the peace-loving Celestrians must reluctantly declare war on the Eldorian Empire. And if they're to have any chance of victory, they're going to need some help. Help which is suspiciously close at hand...