Agunea

Castlevania: Symphony of the Night
A strange but powerful weapon, the Agunea fires a small, nearly-invisible projectile straight ahead. Once it hits, the attack button can be held down, and multiple bolts of lightning will strike the target at the cost of 5 Hearts per lighting bolt. It is an effective weapon against many bosses in Symphony of the Night, particularly the Succubus. Richter's item crash produces a large burst of electricity. There are four Agunea to be found in the game, spread across both castles. It has been described as a "lightning ring" and a "taser" by different people, although there is no definitive answer as to just what the Agunea is, although some suspect it to be a derringer type pistol. Alucard's lightning attack while jumping in Castlevania: Judgment is most likely inspired by his Agunea subweapon in Symphony of the Night, though it cannot be continuously applied. The Agunea was also featured in Castlevania Puzzle: Encore of the Night, as a spell that can be used by Alucard.