Mystara's Lullaby was a machine/musical melody created by the Etymology in 3,300,000,000 BCE and was destroyed in 3,290,999,970 BCE.
Mystara's Lullaby stands alone in its like amongst the many creations of Mystara and the wider Etymology. It seems to be a sort of manufactured musical melody that when played at certain frequencies, influenced the emotions to what ever species that had the ability to hear.
It does this by using a special type of frequency that once the brain makes out into sound, it will make anyone that hears it feel whatever emotion the lullaby is wanting them to feel for the duration of its playing.
The exact melody of the lullaby will vary depending on who hears it, however if the lullaby is attempting to make someone feel happy then it will sound upbeat to them, or if its attempting to make someone feel sad then it will sound somber, and so on. Though one constant is that it sounds like its being played through late 18th century music boxes that existed on planet Earth.
The melody would be created with the use of a machine referred to as the "Music Box" by Mystara for obvious reasons, and it would randomly generate musical notes at different frequencies that would make each individual hear music that would seem to be specifically made for them.
This was created by Mystara, one of the Ten Supreme Authorities, in the hopes that the Etymology could use it to pacify various groups that posed a threat to the civilization, which it turned out to be quite successful in. However due to the events of the "Time of Sorrow" the machine responsible for the melody would be destroyed.
Mystara's Lullaby would be created, unsurprisingly, by Mystara herself, in response to the growing hostilities of the Propitia species, as they still remained defiant and unhappy that they were seemingly forced to join the Etymology in 3,300,000,002 BCE.
Thus, not wanting to commit any military resources to this seemly insignificant issue, but still wanting to remain in control over the species, Mystara thought of an idea. She would begin to wonder if she could create a special type of sound that could pacify all that would hear it, as well as making them feel any kind of emotion they wanted them to feel at any given time. And in the short time frame of two standard years, she would create what we would now call: Mystara's Lullaby.
The Etymology would quickly test it on the Propitia, using large ships across the planets atmosphere equipped with massive speakers, they would begin playing Mystara's Lullaby at the specific frequency to make one feel contentment, and within mere minutes, all on planet Abitur would begin to feel the aforementioned emotion, and once the melody had stopped, all that heard it would forget why they were angry in the first place, in a way similar to drugging them. As such, the hostilities on the world became nullified, and the Etymology would become quite pleased with this new tool in their arsenal, as they would continue to use it on various worlds for the next few decades.
However, on 3,290,999,970 BCE, the Music Box, while arriving within Póli Ton Theón', would mysteriously activate at the frequency to make one feel all encompassing sorrow, causing the quadrillions on Póli Ton Theón' to break down in a immobilizing state of depression. This would even effect the Ten Supreme Authorities themselves, though Mystara would've made sure that they would have been immune to its effects, they would also be mysteriously placed in this depressive state. Even artificial beings that were capable of feeling emotion would fall under this state as well.
This would be known as the Time of Sorrow and it would last for an entire standard month, until' the Music Box ran out of power. Realizing how powerful and unpredictable this seemingly simple machine was, they quickly destroyed it and Mystara would not attempt anything of its like again, making sure that future generations of the Etymology would be unaware that it even existed in the first place.
Much later, the C.Y.R.E.X in its infancy would discover the logs of the lullaby's creation. And to test its abilities, it would use the plans Mystara used for the Music Box's creation. And with the aforementioned plans it would create a miniature version for itself in 687,543,213 BCE. Once completed, it would listen to the endless randomly generated music it would create, and it's believed that it continues to do so to this day.