Mist

The Mist is a corrupting ether that permeates a lot of the older woods and mountains of Osera and Hesperon. It is within the mist that the Horrors live, and presumably multiply.

The sages of the Seventh Sanctum believe that the Mist is either caused by the Horrors, or alternatively that both are produced through some black magic by the Lethe. Alternatively, some plants may be responsible for producing the Mist, though these would have to be quite rugged since the Mist also hangs low over mountains. Further still, it may be a property of the land itself, as no Mist is known to exist in Zinnabar.