From Destinypedia, the Destiny wiki
Savathûn's Brood Hidden Swarm (presumably, formerly)
High Durability Rapid Movement Shadow Vanish Sword Slam
The Shifting Blade is a Savathûn's Brood Darkblade that acts as a guard to Savathûn's Witness during the third week of Interference.
The Blade as it stands before the Guardian.
The Blade as it protects the Witness of Savathûn.