Cloaking device
From The Heretic Knowledge Vault
Unidentified magical thingie that allows things as large as cities (i.e., Tsuirakushiti) to be concealed from the outside world. We don't know how it works (or worked) or whether anyone else has (had) one, but we do know that Tsuirakushiti's doesn't work so well any more, following a small incident involving Luminosita. Cause-and-effect relationships, and exact chronology, in all this are still being worked out.
The elves also had some kind of magical barrier that kept their capital city (Praenubilus Astu) and other elven lands walled off from smelly humans for a long time, but Luminosita took care of that too. We don't know whether their barrier is the same thing as the cloaking device used at Tsuirakushiti, however. Probably not; the implication is that Veracia knew about the elven homelands and the barrier all along, while Tsuirakushiti was entirely out of sight, out of mind.