Once upon a time, there were two worlds. They were connected to each other through a number of small holes that allowed communication to flow between inhabitants of each realm, as if the worlds were breathing through these holes. However, they had a tendency to close up, so guardians stood next to each one to keep them open. The guardians were called “Custos Cavum.” They took the form of seals and had large front teeth, which they used to gnaw the holes to prevent them from closing up.

Whenever a Custos Cavum felt the generation of a new hole somewhere nearby, it fell into a deep sleep. From the body of the quietly sleeping Custos Cavum grew winged spores called “Unicuses.” These spores took flight and each flew to a new, unprotected hole, where it gave rise to a new Custos Cavum.

As time went on, the people of the two worlds communicated less often, and they began to forget about their peers living across the divide. Their guardians lost their power and died one after another. The holes were allowed to close. When the last Custos Cavum died, the last hole closed, separating the two worlds completely. The existence of the other world was entirely erased from peopleʼs memories.