Replacing one's body is difficult and expensive, but it is a last resort if someone is ruined beyond repair. For species with centralized nervous systems, a brain transplant can keep the brain alive until a cloned body is ready to accept it. The traumatic experience has permanent ramifications and is impossible for dozens of species. Even for those who avoid grievous injury to their bodies, two hundred years of consciousness is the upper limit. Distinct from the physical brain, the mind breaks down regardless of an individual's health. With few exceptions, inhabitants of advanced societies die once their minds collapse.
While some forms of thaumaturgy can provide moderate increases in lifespan, avoiding mental collapse this way proves difficult. The solution is the removal of the pylon. The pylon is the gateway between the non-physical mind and the brain. To destroy a pylon, a powerful user of Thaumaturgy, a world-class magus, executes the procedure at great expense. Through careful manipulation, a substitute Faux Pylon links the mind to an artificial brain. Two problems disappear—the individual abandons an organic body, and they replace the main cause of mental degradation. The resulting being is a Nachleben, deriving from the Boreal Basic word for "Afterlife." Nachleben technology is related to Eidonic Intertial Warding and grimoires.
These uploaded minds have one additional benefit—immunity to Ego Decay. Minds are highly elastic and can easily shed even fundamental information. In other words, spending one's life in a virtual world causes the mind to forget its pylon, a fatal process. Periodic reminders of one's actual body prevent total immersion but also maintain this connection. Typically, over half of one's waking hours should take place in reality or with awareness of it, but sleep usually takes up most of one's time spent "away" from the body. Faux Pylons actively hold onto their host mind, allowing Nachleben to bypass ego decay.
Nachleben hold onto the mind via complex conceptual containment. Mathematical models, constantly adapting and unique to each individual, serve this purpose. Most computation relies on the manipulation of electrons, but more advanced quantum computers have a small influence on the Noosphere, the realm of ideals. While most computations are random and cannot serve to create a conceptual structure, the particular mathematical models used can create robust frameworks not unlike spirits. These models produce numerological memeplexes which, while at the peak of current technology, are far simpler than the spirits that nature spontaneously creates. They can be thought of as boxes that contain a mind. The mind within a Nachleben learns how to subconsciously interact with its "box," thus interacting with the physical universe.
Most Nachleben require hundreds of gigawatts of energy, but far more advanced models, such as those found on Crimwol promise megawatt Nachleben. The ancient civilization that made these highly efficient Nachleben, Tech Egealta, has long since collapsed and its secrets lost.
Some nations, such as the Oralat Virtual Utopia, spent centuries uploading their population. Before this civilization, most Nachleben were leaders or tremendously wealthy individuals. A dynasty of Nachleben ruled Erstes Konsortium for centuries and, true to the nature of Nachleben, paid little attention to the actual universe. Kalliolel, a powerful semantic dynamo, became a proper intelligent being by convincing millions to become Nachleben and join its network.
Nachleben are known for developing eccentric or unstable personalities, likely due to imperfections in the modern technology. While once a powerful force in society, they have hardly been relevant this past millennium. New Nachleben are uncommon as a cultural stigma against "mind uploading" has emerged. While philosophers argue about whether or not becoming a Nachleben constitutes a kind of death, the common conception is that becoming a Nachleben means death.