The Boogey Conundrum is part of the background of Ashen Stars. The Combine - something like Star Trek's United Federation of Planets - fought a devastating war against the Mohilar The war started seventeen years ago and ended seven years ago. Since then, nobody in the Combine can remember details about the Mohilar Their culture, weapons, language, tactics, and even their appearance is unknown. Trying to recall these facts leads to a state of confusion. Records exist, but accessing those records causes black outs and periods of missing time. Even trying to research the effect itself is problematic. In the end, the Combine just slapped the label "Boogey Conundrum" on the effect and called it a day.
Ashen Stars author Robin D Laws states in the rulebook that the Boogey Conundrum is not part of a metaplot. It is entirely up to GMs and players to work out what it is within their own campaigns. He does offer some suggestions, but no definative answers.
Below are three ideas I fleshed out a little. None of these ideas are official, but certain elements requite a knowledge of the game's background.
Civil War Cover Up
There was never a race named the Mohilar They never showed up with fleets and living weapons, never laid waste to the Combine, and never disappeared. It was all a cover story cooked up to hide a devastating secret - the Combine went to war with itself.
There were always tensions within the Combine. The Seven Peoples had all fought each other at one time or another. Their interests did not always align perfectly. Cooperation had brought great prosperity, but for how long?
How did it start? Perhaps the careful control of the Balla slipped. Maybe the newly developed Cybes were a step too far. Durugh trickery is an easy answer. The ambition and extremism of the Humans, fueled by their boundless energy, may have become an intolerable threat to the other races. The Tavak could have struck at the other races to preserve the Combine before it tore itself apart. Or the Kch-Thk might have just gotten really hungry. In any event, the Combine shattered under the stresses placed on it.
All of the races found themselves fighting for survival. The early war's surgical strikes failed to be the decisive. The middle of the war saw a steady escalation as fleets maneuvered and alliances were forged and broken. By the end of the war, there was only horror as population centers were bombarded out of existence.
At the end of a decade of war, somebody made a deal with the Vas Kra. The cosmic consciousness had watched the conflict with sadness as the once-proud Combine committed suicide. The Vas Kra could not reverse the damage or restore the lives lost - they were powerful, but not gods. What they could do was alter the memories of the survivors. Blame for the devastation would be cast on a race of mysterious invaders. It was hoped that this - and the implied threat of their return - would unite the Combine as it rebuilt.
The Vas Kra knew that it would take almost all of their power to accomplish the task. They did it anyway, becoming the Vas Mal. Their work was imperfect, but good enough to conceal the real reason of the near-destruction of the Combine. Unfortunately, the restored Combine is not as unified as the Vas Kra hoped it would become.
The Mad Gods
D’jellar was not the only Vas Kra to go mad, only the first. More branches of the Vas Kra turned away from the cosmic consciousness to satisfy sadistic urges. The malignancy spread quickly. Soon, the majority of the Vas Kra began to delight in using their powers to torment and destroy.
There seemed to be no defense and no hope as the decade of madness stretched on. Fleets and worlds were wiped away. Countless lives were lost as the Vas Kra amused themselves. The Combine and Durugh formed a desperate alliance, but their depleted forces were helpless against the rampage.
In the end, a way was found to reconfigure the anomaly the Vas Kra used to manipulate reality. It was widened into a gate and a weapon designed to disrupt the energy forms of the Vas Kra was sent through it. The Vas Kra were devolved into the misshapen forms of the Vas Mal.
But the crude weapon had side effects. There was a huge psychic backlash as the Vas Kra fell. The malignancy the drove the Vas Kra mad was itself a cosmic power and found itself devolving with them. Its decade of madness and joy was over, but it would go down fighting. It rode the psychic backlash, ravaging every mind in reach to create a myth. The false story of the Mohilar would serve as a distraction until it could find a way to wield real power again.
The Mohilar Went Home
The Mohilar were rolling over the Combine. The Combine's fleets were pressed up to the wall. Combine worlds burned in the night. Only a little more time and the Mohilar emerge victorious.
Then... they packed up and left.
The Mohilar's armies regrouped, withdrew from the front lines, and boarded their assault craft and transports. The Mohilar reorganized their logistics - dismantling their bases and loading everything up for the trip home. The warships of the fleet guarded the evacuation effort. Slow moving cargo ships joined convoys and turned for the home systems. Nothing was left behind.
The Boogey Conundrum was one of a number of carefully calculated acts designed to slow the Combine's recovery until the Mohilar returned. The bombardment of Earth and the fall of the Vas Kra were other parts of this plan. Leaving some of their living weapons behind was not part of the plan - the Mohilar just couldn't be bothered to gather them all up. A disrupted Combine without the aid of the Vas Kra or even any memories of the Mohilar would be ill-equipped to deal with another invasion.
Why did they go? A military campaign could be called off for any number of reasons.
Politics:
- Loss of popular support back home.
- A restless population or civil war.
- A new set of legitimate leaders who see no point in continuing the conflict.
- A political process that the leaders of the campaign need to go and participate in.
Weird:
- A religious rite that must be observed personally every 10 - 15 years.
- Some biological cycle that has already been delayed for as long as it can.
Practical:
- Ran out of slave troops and their living weapons weren't considered reliable enough.
- Ran out of the unobtainium that their technology runs on.
- Ran out of royal jelly for their queens.
- Ran out of money.
Whatever the reason, the Mohilar left. But they'll be back once they deal with whatever caused them to leave. And the Combine won't be ready.