After all four Amplifiers are charged, a purple Lantern will appear, floating from the Courtroom to the Church or from the Courtroom to the Jail. The player needs to use a grenade to knock the Lantern out of the air, timing it such way that the grenade explodes when it is right next to the Lantern.
The Lantern will fall down on the ground and the player has to pick it up by interacting with it. Subsequently, the player has to go the the Mansion where it has to kill at least 10 Witches to power up the Lantern. Once the Lantern is powered-up, Richtofen will say that you must use it's power to show the way, and the player has to place it on the roof of the Gunsmith Shop.