Nayoman
The Nayoman were a race of genetic hybrids who invaded shortly after the Light ended in the Crucible, they came on various sized Void Ships powered by technology and through the subjugation of a species known as the Void-Baelenes. They came in search for the secrets of Magic as there race was magically numb.
The key feature of the Nayoman is that no one truly knew what they look like, they were a race of genetic hybrids, it was found out that as they invaded other worlds and encountered species they took what they deemed to be the best aspects of them and genetically fused it to there own DNA.
The Nayoman Invasion was very nearly the end of the Crucible many worlds were left in ruins but through combined arms and setting aside of old fights the peoples rallied together and destroyed the Nayoman. Today the Nayoman are completely destroyed, the only remnants left of there existence are ancient hulks floating in the planetary orbits and overgrown rusted out hulks dotting the landscape.
From the Nayoman however the Dwarves of Titan were able to reverse-engineer electrical components and in the aftermath of the Invasion technology advanced exponentially, in fact it is safe to say that without the Nayoman the age of the InterFleck may not have happenned.