Magnetic Sweat Snatchers

The relentless search is on: Find the opal-like sections of a matter transmitter, scattered across a continent. Without them the only human colony-planet dies. The pieces are hidden in the vast deserts, tangled jungles, medieval cities and stark fortresses of this world. They are defended by fanatics. The fifteen sections are technological miracle-workers, more precious than fist-sized diamonds in a colony regressed to the 14th century level. Yet, the various hunters will let nothing in their way.Against humanity's questers race the Morkth, space-traveling xenophobic alien destroyers of Earth. They are determined to destroy all these human vermin, soon. But first they want the matter-transmitter. They want it badly, and they destroy anything that tries to stop them. They have nukes and lasers to the colonists' swords and spears. It's no contest.