Nulien

Nulien is a plane that had reached a high tech level, but much of its tech and civilzation has been lost following years of attacks from "creatures of Elsewhere" that began invading the plane. Nulien is the setting of Experiment[5]: Nulien.

The First Rift
Nulien is a rather small plane, initially only having a few large cities, but despite this its technology advanced to Tech Level 7, developing cars, powerful prosthetics, intelligent AI, and other devices. One citizen of Nulien, known only as The Experimenter, grew tired of the confines of the plane, and wished to travel the Multiverse like the planeswalkers that would occasionally visit the plane. The Experimenter would spend years developing a device to allow them to planeswalk for themselves, but when activated the device began opening rifts all around Nulien that allowed monsters from places unknown into Nulien, but would not let The Experimenter leave the plane. These "creatures of Elsewhere" as they came to be known were unlike anything Nulien had ever seen before, with many of the creatures being gigantic to the people of Nulien, or bringing strange diseases with them that Nulien did not know how to fight. While the efforts to fight back never stopped, the creatures of Elsewhere didn't either, and bit by bit drove Nulien civilization into hiding.

Surviving
The citizens of Nulien splintered into a large number of smaller towns that developed their own governance in any quiet place of the plane they could claim. Some would try to keep their previous civilization alive, some would revel in the collapse of it, some would try to reinvent it for the new world. Groups of scouts from all the towns would investigate areas of Nulien where the creatures of Elsewhere had taken claim, looking for ways to fight back or reclaim lands or spoils that the creatures had evacuated. These scouting groups became the most dangerous profession of the new Nulien, but also the most necessary, as even the quieter areas that the towns had set up in would not be free of the creatures forever.

Experiment Zero
Despite the failure, The Experimenter was still dedicated to using technology to solve this problem and get them off Nulien. While the plane crumbled, they built a robot designed to fight them and eventually be their ticket out. The first version of this robot was Prototype[0], an inhuman robot with considerable speed and power that was able to kill creatures of Elsewhere while taking the heavy damage the creatures could dish out and being immune to their diseases and other effects. While its combat abilities proved sufficient, the frightening gnarled metal of the prototype worried people as much as the creatures themselves. With the help of an unknown planeswalker, The Experimenter redesigned the robot, creating Experiment Zero.

Over the next few months, Experiment Zero would hunt down creatures of Elsewhere across Nulien, reducing the population but still unable to stop new creatures from entering through the rifts across the plane. With the first part of their plan now working, The Experimenter began their next step, attracting planeswalkers to Nulien, and convincing them to donate their spark to Experiment Zero, and eventually after that had failed, stealing their sparks for the robot instead. After implanting five sparks into Experiment Zero, the robot unexpectedly planeswalked away from Nulien. Experiment Zero has not been seen in many months since.