Back Weapons, also known as Sub Arms, are one of the inventions of Ernesti Echvalier. They are additions to a Silhouette Knight that grant it extra arms. The first Silhouette Knight type to feature these arms is the Telestale.
The Sub Arms appear as smaller versions of a Silhouette Knight's two main arms. Their abilities vary based on what they are equipped with:
- Rod Arms each hold a magic rod, and can be used to fire off bolts of energy, just like a normal Silhouette Knight's rod. The Telestale was the first model to feature these, and up to four have been shown on one Silhouette Knight.
- Sword Arms each hold a Silhouette Knight sword, which can be swung and acts like any other sword. The Swordsman Silhouette Knight has two of these.
- Shield Arms each hold a shield, and can be used for defensive maneuvers. The Earlcumber uses these to great effect, and has two Sub Arms that can be operated separately or come together as one massive shield.