From the introduction:
During a barely remembered golden age, a cabal of wizards constructed a series of experimentation chambers, scattered all over the world. To protect the public from accidents, great magical effort buried the chambers deep underground, with no connections at all to the outside world. With their intimate knowledge of the details and location of each chamber, the wizards simply teleported in and out of the laboratories, but their assistants and other minions could not. So the wizards connected the chambers with a network of teleportation circles, to allow minions with the proper keys to move about the labs. The wizards have long since passed and, with them, the knowledge of the lab network. Even the few teleportation circles that would carry their minions into the labs from the surface were destroyed and forgotten. The network remains powerful magic, however, and undulates throughout the world. Occasionally, it malfunctions and “captures” creatures from the surface world, especially when strong magical events occur there. Events like the one that just happened around the PCs, transporting them all into room one...