The Nal'gahary is an extremist movement that originated within the Devore Imperium. It has grown outward from its birthplace, and added members from many Delta Quadrant cultures.
Their stated goal is to remove alien influences from native cultures, including, but not limited to those instigated by the alpha invasion. The Nal'gaharay seek a restoration to a pre invasion community of worlds.
What should be obvious from these statements is one predominant view. Alpha, Beta, and Gamma Quadrant species do not belong here. The Nal'gahary have declared us invaders in this territory of space, and they are opposed to our presence, whether that presence is benign or not. They see us as outsiders, who have affected the balance of power in the quardrant, and they fear OUR expansionist tendencies.
The Nal'gahary Movement is akin to Al-Qaeda in Earth's 21st century. They move in secret, they perform guerilla style, or terror style attacks, then when the time is right, they claim responsibility for their actions. Their senior members are mostly unknown. Those who are known are hidden deep within their own territories. Still their agents perform acts of aggression both far and wide, in the name of the Nal'gaharay.
The Nal'gaharay have no armies, no standing navy, etc. Their movement is not large or strong enough at this point to directly challenge any of the powers that now occupy parts of the Delta Quadrant. They are not tied to any one particular race within the DQ other than possibly, the Devore, though diplomatically the Devore claim no connection to this group. Ships crews or units working with the Nal'gaharay will most likely be predominantly from Delta Quadrant races, either singly or mixed. They may have sympathizers colluding with them which are among us. They may attack ships or stations that are non-DQ in origin or who harbor or do business with them. The Nal'gahary will claim the actions of their agents as a means of declaring their open contempt for invading species and to inspire fear in them. One method of announcing their presence or activity is through the use of the Purity Symbol of the Nal'gahary.