Xanathar is a paranoid beholder who used to run the Xanathar thieves guild before being buried alive by ISIS. This crippled his organization and after digging himself out, he has sworn revenge on them. While not at his full strength he has been carving out another home for himself and after almost dying at the hands of ISIS, he has been contemplating his mortality constantly, so the point that he'll soon become a death tyrant.