Phantom Blade Longsword

This silver handled longsword is covered in arcane glyphs and sigils. Its blade is tinted an eerie greenish color.
As a free action, you can send the blade in and out of the Ethereal Plane, causing it to vanish or appear. While in the ethereal plane, the blade is capable of hitting incorporeal creatures such as ghosts or other spirits, but otherwise does not overcome any other resistance to non magical weapons.
The sword is in the possession of Kara Wyrmwater, gifted to her by Lucien Novelle, and was originally found on Cromwell Island.