The Envsiagers are a group who believes they can manifest radiant powers if they put themselves in situations of extreme danger. At the moment, Shai is the only Envsiager who has manifested radiant abilities.
The party learned in Bavland that the Envsiagers have locations throughout Roshar, and their main location was in Kharbranth.
Kael and Jarro killed Elias, the leader of the Envsiager group, and for the moment it is unclear the status of the remaining locations or the remaining cult members.