Sword of shadows turns illusions into shadows (summons). I tried it in single player... not sure as I didn't explore it but it could be quite strong. Would you consider it a bug?
Wish it was a FW rune. Along with the two UD Soultap things (the Nora Gem and the spell Soul Feed) That being said, is there really any of a reason to cast Soul Feed at 30 Nora on your own dudes, or is it only useful for deleting range from baddies?