Protoss-Nerazim

The Nerazim, or the Dark Templar as they are known to outsiders, is a tribe of protoss who reject the Khala. To demonstrate this they cut their nerve appendages, severing themselves from the psionic communal link. There is a history of mistrust and hatred between the Dark Templar and the Khalai.
The Nerazim are the great tribe to which all Dark Templar belong.

Having cut themselves off from the Khala, the Dark Templar driven by individuality and a thirst for knowledge. Willfully independent, the Dark Templar hold their allegiance primarily to their warrior clans and then to the Nerazim. They tend to be motivated more by personal and tribal bonds than by authority, and hold individuals accountable for their actions.

The clans have scattered across dozens of star systems, often living on small ships. They frequently feud, but band together in the face of threats such as the zerg.

The clans distinguish themselves from each other through unique styles of weapons and armor.

[Psionic Abilities

Dark Templar were taught to hide from the Conclave by the powerful Templar Adun. This ability has been described as "bending light" and "merging with shadows".

Dark Templar wield the energies of the cosmos. These energies are harmful to the zerg cerebrates and Overmind due to the similarities of the cosmic energies they wield. The Dark Templar consider their powers to be to be the "true gifts" of the protoss, and consider the Khala to be diluted and narrowed by the (former) leaders of the protoss. Their own powers are considered "wider".

Dark Templar have the ability to "store" personalities within khaydarin crystals.

Dark Templar are cut off from the preservers; they have no preservers of their own, and their memories cannot be accessed by the preservers.

A group of protoss survivors stranded on Aiur, the Tal'darim, were cut off from the Khala and developed abilities similar to those of the Dark Templar.