Shadow Blade ?

Does this weapon exist, or are people confusing the Fellblade (wich casts a shadow) on the black blade.

I have spent Countless hours in fissure (from nimros to miko) and have never come across a "Shadow Blade"

Any officials wanna clear this up, or if this sword does exist...want to post a screenshot of it ?

I dont think it does..Yet then again, im not sure. I highly doubt it though. Sorry i cant be more official.

They're most likely refering to a Fellblade, which has shadows moving along it's surface...