Agartha

Agartha is a magical firearm, wielded by Albus in the game Order of Ecclesia. The first time it is used in the game, is when Albus steals the three pieces of Dominus. He shoots a max shot (Acerbatus) at Barlowe, who uses a lightning attack to counter it. This gave Albus the opportunity to flee. During the boss fight with Albus, almost all of his attacks are coming from Agartha.

The enchanted pistol can not only fire normal bullets, but is also capable to fire strong magic projectiles. Aside from the above mentioned Acerbatus, the gun can also fire an optical shot (where it concentrates light and dark energy at the tip of the barrel, then shoots the collected energy in a spiral at the target) and Torpor crystals.

It's possible for the wielder of Agartha to use this powers by channeling the energy from a Glyph into the gun. This raises the question if Albus needed it to use moves like the Quadruple Ignis and his warping technique.

Not much is known about Agartha, for example, nobody knows who made it (although it's fairly certain that a member of Ecclesia made it, because it uses the energy from Glyphs to fire enchanted bullets). Furthermore, it's unclear what happened to it when Albus was defeated by Shanoa. Also, since it's the first firearm used by a playable character in the Castlevania series, it raises the possibility that future titles will feature guns.