A beautifully crafted Longsword that appears to be far too advanced for human craft
User can use their bending abilities while wielding the Sword, even in the Spirit World. However, they must be seeds the bender can use while wielding the sword.
Allows the user to channel their bending ability through the sword, even in the spirit world, where the sword, being made by a great spirit and part of both worlds, acts as a conduit for the wielders bending ability from the world of life into the spirit world.
In order to channel the benders worldly abilities it must open a small hole in the veil to create a bridge to the world of life, allowing the bender to use his abilities. The hole draws evil spirits like a beacon, a glimpse of life in the spirit world of death. They seek to use the opening to get through to the world of life and are drawn to whomever uses the sword in the spirit world.
This sword was made by the great spirit of blacksmithing Hephaestus. It was an experimental weapon and he deemed it too dangerous to remain in existence, Before he could destroy it however, it was stolen and taken to the world of life where it hasn’t been seen since.