Natives were an insurgent group based in Skingrad County that operated sometime in the early Fourth Era. Known for their distinctive arrows and modes of attacks, such as beheading the people they ambushed. They were allegedly funded by the Thalmor.
 Nerevarine Cult
The Nerevarine Cult, associated with the Urshilaku Ashlanders, believes that the Tribunal--the three god-kings Vivec, Almalexia and Sotha Sil--are false gods whose power is stolen from the false Dwemer god Akulakhan. Instead of worshipping the Tribunal, the cult is devoted to a mortal leader who died of his wounds after victory in the Battle of Red Mountain: Lord Indoril Nerevar. Vivec was his lieutenant, Almalexia was his queen, and Sotha Sil was his wizardly adviser. The cult also believes that, in the end, Nerevar will return in a new incarnation (the Nerevarine or Incarnate) to reunite the Dunmer and bring down the gods they see to be false.
The cult's most prevalent belief is that the Tribunal morally betrayed Nerevar by going against his dying wishes and advice to take the power of the false Dwemer god, which drew its power from an artifact of ultimate evil. Because of their actions, all the good that they do with their stolen power will eventually be undone or corrupted and they are doomed to weaken and fail over time. Dagoth Ur, however, will become stronger because he uses the same stolen powers for evil.
There are rumors that the Tribunal may have betrayed Nerevar in a greater way by directly backstabbing him themselves to seize the power of Akulakhan. There is no evidence to either support or falsify this rumor, but it is supported by House Dagoth, the rising Sixth House. This is perhaps done in the hope of winning the support of disaffected Dunmer and turning the Nerevarine Cult itself to their support. Fortunately, the Sixth house has not succeeded yet: Dagoth Ur is still viewed, correctly, as the enemy, by the Nerevarine Cult, as much as by the Tribunal Temple.
It is also unclear whether Nerevar's fatal wound was received in his battle against the Dwemer king Dumac, in a subsequent battle against Dagoth Ur, or at the hands of the Tribunal. According to some versions of the history, Dagoth Ur (or Lord Voryn Dagoth, as he was then) stood alongside the Dwemer at the Battle of Red Mountain and betrayed the Chimer under Nerevar during that battle. A more reliable version of the story is that Dagoth Ur fought alongside Nerevar and stole the power of Akulakhan later. Most Dunmer traditions claim that Nerevar and Dagoth came to blows and Nerevar was the victor, though seriously wounded. Some believe that the Tribunal then finished him off; others believe that, for whatever reason, they simply failed to heal him. Whatever the case, Nerevar died at this time. The Tribunal learned how to use Kagrenac's Tools on the Heart of Lorkhan, to steal its divine essence for themselves.
Others who support the Nerevarine Cult believe in throwing the Empire and all foreigners out of Morrowind entirely, whatever the cost. They see a reborn Nerevar as a leader to unite the Dunmer against foreign foes: the thought that the Nerevarine might be a foreigner has not occurred to them, nor have they thought about what this might portend (i.e. that the true enemy is the evil within, not the enemy outside). Fortunately, the Urshilaku are willing to accept this change of interpretation.
 Nightingale Trinity
The Nightingale Trinity, usually called simply the Nightingales, are a trio of highly skilled thieves dedicated to the service of Nocturnal. Members are typically chosen from the higher echelons of the Thieves Guild. Although there is no formal association between the two factions and most guild members are unaware of this arrangement, the Trinity is usually very influential on how the guild operates (Nightingales even claim to be the source of the guild's phrase "walk with the shadows").
Members of the order take the Oath: the Skeleton Key must remain at the Twilight Sepulcher, the Temple of Nocturnal, which must be protected from all threats, even in death, until Nocturnal accepts the spirit of a Nightingale into the Evergloam, her plane of Oblivion. In return, Nightingales use the abilities granted to them for whatever they see fit to do in life. Contrary to popularized misconceptions, the Oath is considered a business transaction rather than a religious matter. While most members certainly take the Oath very seriously, they are not worshipping Nocturnal as a deity, but respecting her as the patron of thieves.