Jagex has stated that with the demon slayer equipment you will "get a boost to damage dealt and experience gained while fighting demons for each piece of the gear you equip. A full set of the gear makes the crossbows the same as their dragon equivalents when fighting demons". Wearing one piece of the demon slayer equipment while killing demons will give 2% more experience in the chosen combat style. Equipping the full set will give a 14% total increase to experience gained. They appear in the Adventurer's Log only if dropped by a Kal'gerion demon.