The Sickle
Aurelia, the Queen of Dalkia, and her sickle, the Black Widow
The sickle discipline is basically a variation of Ivy's battle style. Like Ivy's Valentine sword, it is flexible and can deal damage at both short range and long range. The only difference is although the sickle can come in two states like Ivy's sword (in the sickle's case, normal state and whip state), the player cannot manually control what state the sickle is in. Some attacks use the short range normal state, while other attacks utilize the long range whip state. It can be noted also that the sickle discipline uses stances that resemble Ivy's stances from Soulcalibur II (particularly Spiral Serenade and Spiral Tribute). The one unique trait of this discipline though is that it is the only weapon in the whole Soul series that does not have an unblockable attack in its moveset (although one particular attack becomes unblockable if the Soul Charge is first executed).
The sickle discipline is represented by the bonus character Aurelia, and can be found in the Thief, Ninja, and Samurai classes (all of which the player needs to level with 20+ times to make it accessible).