Possibly named after the German chemist named Paracelsus, an early pioneer in the field of toxicology.
It is quite clearly not a sword, but an incredibly large Rail Cannon. A rail cannon is designed to fire projectiles at an extremely high velocity. It was developed by the US Military in order to disable any Umbrella B.O.W. that cannot be stopped by normal means. It was installed in Raccoon City's Incineration Disposal Plant, connected to an energy supply and three additional batteries. The batteries are removable, and indeed they are designed to disconnect from the cannon once it has been fired. As a safety measure they must be re-inserted to continue use.
The cannon is operated by a nearby terminal, and once fired it requires a recharge, as an enormous amount of energy is required to fire a 'shot'.
It has been shown to be capable of destroying any B.O.W. (Bio-Organic Weapon), given enough shots are able to be fired and they hit.
In
Resident Evil 3: Nemesis, this is used by
Jill Valentine to kill the
Nemesis T-Type. Depending on how much damage Nemesis has incurred through weapons fire, it will take between 1 and 3 shots to kill it. It's clear the weapon has been used before to kill other Tyrants based on the dead ones in the room.
In Resident Evil 3 (Remake), the Railgun is completely different - it has been re-imagined as a portable rechargeable rail cannon named the FINGeR (Ferromagnetic Infantry-use Next Generation Railgun)