A vallorn seems to be a malignant hostile magical ecosystem.

Overview

The vallorn appeared as part of the disaster that overthrew the cities of a nation named as 'Terunael' in Navarr legends, which may have covered much of the land which is now Empire. From the hearts of those cities, abundant greenery spread, a sick, infectious wave of life that cracked and crumbled stone, shot great trees up through streets and buildings, and warped, twisted and destroyed most of the inhabitants of those cities, scattering the others to the wind.

As the refugees attempted to claim back their lands, they discovered that around the core of each city, areas of superabundant, warped life had appeared, resistant to all efforts to destroy them. These were named vallorn.

A vallorn seems to be a malignant hostile magical ecosystem -- an area deep in the heart of a forest where even the Navarr fear to tread. Inside them are monstrous plants, the spores of which mutate living creatures that are exposed over many months. Even the air is different within the vallorn, weakening those who enter as if they were breathing mild poison. The plants that grow there often have supernatural capabilities; chaos fruit are an example of vegetation that has been infused both with vallorn essence and powerful Spring magic but there are many others. Some of the plants are even predators in their own right.