The mindhunters are a mysterious group of psions who live in the oceans of the Shadowfel. They have presumably crossed over into the oceans of the Fadelands on occasion, as the Illud believed them to be sufficiently noteworthy to include in Hero Tale. In fact, the Kua Toa are so concerned about the Mindhunter threat that all monitors, regardless of faction, are under standing orders to hunt down and kill any mindhunters they become aware of, regardless of any other missions they may be on.
According to the Rahjs, the mindhunters are constantly aware of the thoughts of all living things and so wish to snuff them out so as to be at peace. To this end, they have allied themselves with Swayne, although why they are not bothered by his thoughts (or if they plan to betray him) is still unclear. It is also unclear as to whether or not they are related to mindflayers, who are conspicuous by their absense from the TDDC universe.
Mind control Edit
Mindhunter mind control is so powerful that they can automatically control anybody without a will save unless there are two, overlapping, layers of mind blank. And even then the target is taken over if they fail their will save. An anti-magic field would prevent them from taking control, but once they have control the domination will not be broken by the field. It seems if you are able to somehow stack three mind blanks on yourself you are immune to their domination. (Though that doesn't stop them from using their mind control on other people…