Keel-Verezy

The Keel-Verezy are a race often mentioned to The Captain by Melnorme Trade Master Greenish in their dealings during the Second War, which appear to have had longstanding commerce with the Melnorme, including providing the Inevitably Successful in All Circumstances with a weapon system for self-defense, yet mysteriously remain undetectable or unreachable for other civilizations. On one occasion, when The Flagship approached the Inevitably Successful in All Circumstances to initiate trade, Greenish accused The Captain of having almost collided with a Keel-Verezy ship. Greenish was at first shocked at The Captain's irresponsibility, then remembered that The Captain's was unable to detect the Keel-Verezy, after which he let the subject drop, refusing to say more. When Greenish did speak about the Keel-Verezy, he claimed that a Keel-Verezy captain with which he was friendly had expressed great interest in Humanity's struggle to free itself from the Hierarchy, but believed that exposing themselves to the Humans would frighten them.

Whether they are truly exist or not (most likely, though, the Melnorme really believe that they are real, as mentioning that their weapon system is bought instead of discovered is not a good way to intimidate The Captain), the truth about Keel-Verezy will have to remain a mystery for now.

From the 2007 IRC chat with Toys for Bob (robot is Fred Ford, PR3 is Paul Reiche III):

00:28 <+Valaggar> Who are the Keel-Verezy? (At least give us a hint)

00:29 <+PR3> Keel-Verezy seem like some kind of horrible evil spirit that are invisible and can fly spaceships.

00:30 <+PR3> (furiously checking uqm.stack) But they are friendly... and evil. And invisible.