Soul Weapons are supernatural weapons that can be freely summoned by the Clan leaders] and the Lord. Soul weapons are the symbol of a Clan Leader's office: every clan leader and the Lord possesses a soul weapon, and only they can wield them. However, there are several exceptions to these general rules. Rael Kertia is not a clan leader but owns an incomplete soul weapon. Cadis Etrama Di Raizel], the True Noblesse is the sole high-ranking noble official who does not possess a soul weapon. The Noblesse is so powerful that his own "noble blood and soul," are his power and in their fully released state, are considered to be his soul weapon. Frankenstein is a human who owns and uses an artificial soul weapon. Regis K. Landegre was able to summon Regasus out of sheer willpower when his Rael was in trouble.
The origin of the term "soul weapon" comes from the fact that the previous wielder of the weapon leaves his or her soul and powers abiding within the weapon when they pass away, as part of the blood heir's inheritance. This way, they pass on their will and beliefs through these weapons. Soul weapons become more powerful with each passing generation, due to the accumulation of new souls and thus, the addition of more power.
A soul weapon amplifies the user's power and parameters drastically and usually has special abilities that suit their respective clans. However, it has been stated that soul weapons do not add power to the bearer of the weapon in the same way that a person wielding a sword gets additional power and abilities (such as additional reach and cutting ability). Rather, soul weapons are a very part of the wielder and embody the office to which the wielder holds, as well as it being the main part of their blood inheritance. Wielding and mastering a soul weapon makes the wielder complete and whole. A noble clan leader or Lord that possesses an incomplete soul weapon is said to be incomplete themselves, akin to a werewolf lacking claws.