Krall was an acolyte of Gellert Grindelwald in the 1920s (CG).
Prior to 1927 Krall joined Gellert Grindelwald and became one of his six trusted acolytes. He assisted Grindelwald in securing a home in Paris along with the other acolytes. Grindelwald questioned Krall’s loyalty at one point during the occupation of the Paris house when the acolyte expressed impatience with the pace of Grindelwald’s plan and its perceived inefficiency. Krall later hesitated when the other acolytes walked through a circle of black flames to join their leader. Krall finally did decide to follow the other acolytes, but he was “consumed” by the fire when he tried to enter the circle (CG).
According to "Fantastic Beasts: The Crimes of Grindelwald: Movie Magic" by Jody Revensen, Krall's wand "has a silver tip."