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 Heart of Lorkhan. The Ashlander cult is devoted to a prophecy by Azura; that Lord Indoril Nerevar will return to cast down the Tribunal as false gods, expel the foreigners from Morrowind and unite the Dunmer.
The cult's most prevalent belief is that the Tribunal betrayed Nerevar. And that because the source of their godhood; The Heart of Lorkhan is also the power behind Dagoth Ur, the Tribunal could never truly defeat him.
The Urshilaku Ashlanders believe that the Tribunal murdered Nerevar to seize the power of The Heart of Lorkhan. The Ashlanders trace that belief to the allegations of Alandro Sul who was shield-companion to Nerevar.
It is 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, Voryn Dagoth (later know as Dagoth Ur) 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 Voryn Dagoth fought alongside Nerevar and stole the power of the Heart of Lorkhan 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, and stole it's divine essence for themselves.