"We serve the Imperium, the Inquisition, and the Emperor. What one will not kill, the others certainly shall." - Grand Master Erdelyi, explaining his faith to his brothers.
Grand Master Erdelyi is one of the most powerful psykers the Grey Knights have ever known. Said to be of Alpha-grade psychic abilities and powers, he slaughters the enemies of the Imperium with both force and mind. He has served the Imperium for over 300 years. His wargear includes a Nemesis Daemon Hammer named, by himself, Doombringer. This hammer is impregnated with his own formidable psychic powers. The power within it is such that it may increase the power of the blows by tenfold, being able to slaughter Greater Daemons with ease.