Into Twilight (Viceroy’s Pride #1)

All known aliens focus on the arcane. Upon learning of magic, their technological progress all but halted as great voidships spread their colonies across the galaxy. For all of Earth’s military might, their only hope is to incorporate the alien’s magic into technology, to use the enemy’s own tools to fight them.

The government is dead-set on transforming magic into a standard-issue weapon. That means finding monsters and harvesting their mana, usually after sticking them with a sword. Despite his better judgement, and the world on his shoulders, Daniel leaves Earth behind to bring them back a future.