Mentalist

Mentalists are psychic mages. Their possession of the psychic gene allows them to innately draw energy from the nether realm, through which they perform their spells and harness their psychic powers. Because they open paths from reality to the nether, they always endanger their souls and, worse still, all those around them.
Mentalists are ruthlessly policed. Only Espers are permitted to wield psychic powers, and even then only after years of rigorous training. All other psychics are considered hedge mages and hunted by the Falconers. While non-Esper mentalists (and other psychic mages) are possible, they must be secretive about their use of psychic power.
Those who are caught face a terrible choice. They may surrender, be sterilized, and either be sent to the psychic concentration camp on Vinus, called Bastion's End, or be lobotomized and have the removed portion of their brain replaced with a computer, both to regulate their power and prevent them from being healed. Those who resist, or are deemed too dangerous to be allowed to live, are killed outright, then their souls destroyed so that they can never be resurrected.
Psychics born with any chaos mutation, or who have learned any amount of arcane magic, are always considered too dangerous to be allowed to live.

Classes

Psychonauts, the default mentalist
Adepts, fallen paladin esoteric blades who've retained some of their training
Arcane Charlatans, mentalists that pretend to be wizards, but risk being mistaken for cabalists
Astral Seekers (Espers only), studious psychics that incorporate a wizard's arcane exploits and academic discipline, but are not distinguished by the Falconers as any different than cabalists
Oracles, divinely-touched psychics who add cleric spells to their list of options

Recommended Prestige Classes

Grand Mentalists
Cyborgs
Hag Matriarchs
Living Legends
Rusalka Lords
Troll Patriarchs
Umbralites
Vampire Lords