Bosetor

Bosetor are portals to the Shadow Realm. They are usually only found on Kobos during the winter months, particularly midwinter. A chill emits from these portals, as does the very negative energy that fuels the undead. Permanent bosetors are marked with pestilence and blight. On Seaudyr, they're most often found in the southeastern portion of the continent, in the canton of Prunyth.
These make life difficult and rather hazardous, so as a warning, cartographers put this symbol on the map:

Manifestation

Bosetor are invisible after a fashion. They are marked by the deepest darkness, and in their presence, shadows are darker and moods are bleaker. The closer to a bosetor, the less life can flourish aside from diseases and scavengers.

Type

Metaphysical, Arcane