From the Atlas:
Thalan: Non-corporeal; Mentalists. Lifespan: immortal.
A strange race which may not even be native to Kulthea, the Thalan are a people who are not exactly immortal, yet their souls remain in the universe of mortals forever. A scroll in the Library of Nomikos, a transcription of a recounding by the Loremaster Andraax, describes some of their peculiar aspects. In fact the Thalan are alien beings who came to Kulthea long ago. They cannot live outside of a body, though that body can be either a living being or a specially prepared inanimate ‘vessel.’ In this way they act as a sort of symbiont and the being is a host.
Thalan are able to transfer from one body to another, but they prefer to possess a child in the womb; in this way they can actually alter the child physically to better conform to their needs. The ‘host’ psyche is also more easily repressed and kept permanently passive.
The Thalan retains all of its Mentalist powers as it switches from body to body. The only way to kill a Thalan is to kill the host in a situation where it cannot flee to another host or a magical vessel.
It needs to be within about ten feet of either to switch. It is almost impossible to detect the symbiont in a host if the Thalan does not wish it; however it is able to create an aura around the body and make the eyes appear to ‘glow’ if it desires to impress or frighten lesser beings.
For me, it seems that Thalan can be good or bad, the ones with the Alliance seems that are making a social experiment than any other thing.
And also it's clear that they don't destroy the mind of the host but repress it while the host is possesed, and looking at their children (we can discuss about ethics here) it's more like a clone that is not allowed to develop his own mind.
In Jaiman I remember the Loremaster Hernae that was also a Thalan and not a bad guy.
