Mana is a blue charged matter, capable of generating tremendous power. It originates from another dimension where there is nothing BUT that stuff. when highly concentrated it becomes a volatile substance, able to be weaponized, often fired as small fast blobs of the stuff. It weakens the bonds between molecules and elements, separating them into their base forms. Pure metals are more resistant to the Mana's adverse effects, but it still causes them to be extremely brittle, allowing even a human's average kick to crack afflicted areas.
Generally this is used more in space, as when it atmosphere the power of Mana weaponry is greatly diminished due to all the molecules and such hanging around.