Firearms were once called the king of weapons. A bullet fired from a gun carried extraordinary force. However, what made these bullets lethal was their extremely small surface area.
They were many times more lethal than arrows shot from bows, or other projectile weapons, mostly because of their penetrative potential. Depending on the strength of the firearm and the potency of the gunpowder in the firearm, a bullet could even blow through a very thick sheet of metal.
In this case, when magic became involved, the need for things like gunpowder vanished. Instead, Cain made use of the magical properties of numerous magical ores and stones to simulate the thrust of a bullet.
Faced with something so sinister, the guards fell like flies. Swimming through the crowd, their swords couldn't touch him. Instead, his bullets always found their mark, either maiming them or outright just killing them.