The Red Queen is a version of a specially designed weapon used by the Order of the Sword created by their chief scientist Agnus. It is unique in its motorcycle type accelerator handle which can be used to rev it up to release a flaming propellant along the blade with a powerful strike. However, it is later shown that Credo too, has a handle similar to Nero's but no evidence to show it is used for the same purpose.
The Red Queen itself is specially modified by Nero allowing it to be revved-up three times and this entire build up of exhaust can be released all at once for a single powerful blow or with separate strikes. This and several other modifications makes the Red Queen nearly impossible for anyone but Nero to wield[1]. Judging by the shape of its blade, the Red Queen is more than likely modeled after the German Grosses Messer (lit. "big knife").
