Setsuna's blade of Retribution (WIP)

Name: Shoukyaku
Appearance: Shoukyaku is a massive blade that is long but thin. It's blade is black steel with red symbols engraved into it's side. The hilt is imbedded with different jewels as a tribute to the different elements.
Rank: C
Special Abilities: The symbgols on the side are have special powers. They allow the blade to change to whatever length Setsuna requires. Also this weapon is not just a sword, it is alive. Setsuna put part of his own soul into this balde. As a result only Setsuna is able to weild it.
Origin: (give us the history of this weapon, how your character received it and if any modifications were made to this weapon. everything counts)