Whoever can come up with the coolest artifact for their universe will have said world be the setting for our prologue.
The notes of Dr. HondaThe Endedverse is known to have many relics, that even in their decaying state, show the technological marvels of the long-gone civilization. The advances made in the field of artificial intelligence in particular eclipse even many of the spaceborne universes, and the implications of how it was made could awnser many questions about the origin and nature of life itself. Not to mention, drive a technological singularity much like the one the Endedverse was on the cusp of.
Doctor Honda Haruko (本田 陽子)* was perhaps the single most important individual known for the creation of the first quantum computer. Rotting newspaper clips name her, at the time only a recently tenured professor at Tōkyō Daigaku (東京大学), reaching a breakthrough in the practical construction of such a computer, discovering a set of equations which virtually eliminated quantum decoherence. The fact a (realitvely) young, and female, researcher was the one to discover the breakthrough made Dr. Honda an overnight sensation in Japanese and international headlines. She would win the 1980** Fields Medal, and eventually the Nobel Prize in Physics in 1987.
However, Dr. Honda felt like she was not getting the proper respect that she deserved within the university, especially with rampart sexism within the academic bureaucracy. To make matters more interesting, she was a member of the Nihon Kyōsan-tō (日本共産党), or the Japanese Communist Party, and was an ardent true believer at that. While the whole world was using her freely published findings in order to accelerate the development of quantum computers, recent archeological work by the Initiative has led to the belief she was secretly leaking more confidential research to the KGB. This would eventually culiminate to a very public defection to the Soviet Union, who had used her work combined with native Soviet researchers to build robots that could largely automate portions of the lagging Soviet economy.
In 1991, Dr. Honda would very publicly defect to the Soviet Union, a major scandal which almost put the world into a nuclear standoff. However, the armageddeon that struck the world would not come for another six years. The Soviet Union, now rivaling Japan as the two "quantum superpowers" (with the USA lagging behind at a distant third, although still the leading "atomic superpower"), quickly used its miraculous economic explosion to keep the Eastern Bloc together, as new wealth trickled down into the rest of Eastern Europe. Dr. Honda would take residence in Leningrad, and become tenured at the Leningrad State University.
All we know after that is that the world eventually collasped on itself circa 1997. We do not know much details about Dr. Honda's personal life, besides that she would occasionally take trips back to Japan in order to meet with her family. This means that her last whereabouts could be as far in a range from anywhere from the ruins of Leningrad to the ruins of Tōkyō, and that's assuming we can even identify which specific city corresponds to which specific ruins. And if some looters got their hands on it within the chaos of whatever ended the world up to the extinction of all of its lifeforms, it could be somewhere we have no idea where to even look for.
But whoever can find these notes, would find themselves armed with some of the most sought-after information in the entire Multiverse. It would kickstart a technological revolution in any universe that has the tools to construct automations, which could theoretically either bring a multiversial golden age, or destroy it all like it did with the Endedverse.
*Or, in western naming conventions, Haruko Honda
**All dates are in solar cycles, arbitrarily chosen in reference to some historical event within the Endedverse