Thir
Thir is the primary religion of Dragons. The name comes from the Draconique word for “three”, reflecting their belief in the three Premiers Dragons, and three levels of divinity: the Progenitors, the Dieux Dragon, and the Sovereigns.
The Dieux Dragon of Thir are: Io, Aasterinian, Astilabor, Bahamut, Chronepsis, Falazure, Garyx, Hlal, Lendys, Tamara, and Tiamat. Each has a constellation in the sky, and they are generally believed to exist beyond Eberron's standard planes. (Though Tiamat is known to be in Khyber.) According to Thir, the Dieux Dragon are only concerned with dragons - lesser creatures such as Humains and Elfes are the purview of Sovereigns.
Thdu s concept of Sovereigns generally corresponds to the fifteen members Légion Souveraine and the Sombres Six. Followers of Thir believe that a Dragon who comes to embody a fundamental concept can ascend to one of 15 positions of the Sovereign Archetypes, causing the previous Sovereign to occupy that position to ascend to the same place the other Dieux Dragon have.
Followers of Thir believe that the Prophétie Draconique is a product of the Premiers Dragons and their diverging desires for the reality they shaped. This ties into their belief in the cyclical nature of creation, which is a central tenant of Thir. They believe that once the Prophétie Draconique has run its course, three new progenitors will be chosen from among the Dieux Dragon, and the Sovereigns of this reality will become the Dieux Dragon of the next reality.