Fan-Faili is a ‘Holy Weapon’ wielded by the knight Railith in the story Eu-Knight. Fan-Faili is a customized railgun similar to a Silvershot rifle. In the story it is regarded as a ‘holy weapon’ due to its tremendous destructive power in a world that uses steel weapons.
Railith was trained on all weapons but her cooler, calculating attitude suited her towards this sniper rifle. Given a majority of the enemies they fight often wear shields her weapon ironically is not as good as its destructive power would indicate. When an enemy does not have a shield she easily, and literally, blows them apart.
Given her partnership with Dirx, she will shoot an enemy and either kill them outright, or the shower of sparks off their ‘aura’ (shield) is enough for Dirx to close the distance with his I.I. blade to bust through the shield. Against non-shielded enemies they simply do not stand a chance given she can shoot literally farther than she can see.