Lancer came under Zaidoun's tutelage years before Zaidoun encountered Diamond Darling. He studied under Zaidoun for a considerable amount of time, but the two eventually parted ways. Lancer was an excellent student and had a natural proficiency for Gun Tongue.
Darling speculates, from what Zaidoun has told her of Lancer, that he was killed during a mishap while attempting to use an advanced Gun Tongue incantation. She has no solid evidence of this, however, and Zaidoun rarely spoke of him in their time together.