Complex sentence: In 3028 A.D. humanity has mastered deep space travel and interacted with several alien species, when a human experimental discovery called "Project Titan" alarms the antagonist Drej, who attack the human race.
Split into simpler sentences: In 3028 A.D. humanity has mastered deep space travel and interacted with several alien species. A human invention called "Project Titan" alarms the antagonist alien species the Drej, who attack the human race.