For a weapon to become a Death Scythe, they must hunt and eat ninety-nine human souls that are on Shinigami's List and one witch soul.In the anime, there is no list; instead, the weapons have to eat ninety-nine kishin eggs and one witch soul. By consuming the final witch's soul, a Death Scythe is granted numerous powerful abilities. This is achieved by the advanced wavelength control gained from the witch's soul obtained, which can bestow "almost magical-like abilities" and manifest additional special abilities.
Among these abilities is form manipulation, which allows a Death Scythe to change the shape of their Weapon form. This ability is noted as not only a standard trait but also one of the most basic. However, form manipulation can give rise to powerful and useful techniques, such as when Soul demonstrated the power to create wings of light, for flight, by focusing on achieving the same goal as Maka. Death Scythes can also "sprout" weapon parts from their body without having to replace any body parts.
The term "Death Weapon" itself is not present within the original Japanese version of Soul Eater. It is assumed at this time to be an original word for the English Yen Press version. It's possible the term was created to separate the Death Scythe weapon class from the individual, Spirit Albarn, and his transformation name.