When you complete a Champion's Challenge, Larxus rewards you with 200 to 6000 Slayer and Constitution experience, depending on which Champion was defeated. If it is your first challenge (including the training challenge), Larxus will also reward you with a bag of Calling beads. These can be used to summon a Banner carrier, which follows you and displays those champions that you have defeated. If the Calling beads are lost, they can be reobtained for free from Larxus.