My campaign culled from the lyrics of songs by Tinarawen has the players archaeologist mentor murdered to silence his discovery of the mythical Nadir settlement mentioned in corebook. Further evidence collected suggests that the Nadir were lost in time and arrived in the third horizon millennia ago.
They evolved into the Portal Builders and that there are nine Emissaries, their descendants, who are the Icons.
This evidence could shatter political control, faith, etc..