Miasma
Miasma (瘴気) means "a highly unpleasant or unhealthy smell or vapor" in the common term, but in Vilous, it's referred to some sort of gas produced by some Talyxian plants in northern and eastern regions of Planet Tal. It has mind altering properties to Eltus races.
There are differences on nature and its influence between Northern miasma and Eastern miasma. As a common feature though, regarding the influence on the Eltus race it is generally said to bring some kind of bad effect on the spirit and the brain like a feeling of drunkenness.
In any case, Eltus people need an equipment such as gas mask or "sensation filter" to keep decent sense and sanity when visit place that there's risk of suction of miasma.
Northern miasma
Some part of Northern primeval Talyxian forests are filled with strong miasma from the distant past. It is said that it affects the people's brain over a long period of time. As its effect, as can be seen in primitive Northern sergals behavior, it's said that hinders people to have a strong will and thinking faculty of their own. As the result, it makes people have adapted to their own near insanity and aberrant situation.