Complex sentence: Why do they fight us?! The player then fights through a number of enemy empires, gaining new technologies and rescuing allies along the way, to find that their enemies produced the greys, despite the danger that the greys would destroy them too.
Split into simpler sentences: Why do they fight us?! The player seeks to find the source of the greys, and encounters other seed empires. They then fights through a number of enemy empires, gaining new technologies and rescuing allies along the way, to find that their enemies produced the greys, despite the danger that the greys would destroy them too.