My copy of #ExploringEberron finally arrived; it’s pretty great. A question came up while looking at the timeline: if House Kundarak wasn’t recognized and inducted until ~1600 years after the Twelve were established, were the Twelve called the Eleven before that? From Dragonmarked: "Though there were only ten dragonmarked houses at the time, the architect Alder d’Cannith convinced the committee to name the institute the Twelve, based on his belief that there were twelve true dragonmarks in addition to the shattered Mark of Death."
— Keith Baker (@HellcowKeith) September 1, 2020
It's actually called out on page 245 of the original 3.5 ECS, as well. Alder d'Cannith was using the number of moons and planes as his guide, and the Mark of Death had been lost—so he concluded that it was a 13-1 situation, even if two marks were yet to be found.
— Keith Baker (@HellcowKeith) September 1, 2020