Stronghold is Steelheart's bird partner.
After the creation of Sky Shadow, the SilverHawks created avian partners to assist them. These four robotic birds were called the Fighting Hawks. Stronghold is one of the four Fighting Hawks, created to respond to greater threats of the Limbo Mob. He was created to specifically support Steelheart.
Stronghold is a steel gray hawk robot that matches his partner. He is capable of flight both in atmosphere and in the "space" of Limbo. He has powerful talons capable of pierce most metals. As his name suggests, he has a tremendous grip and can lift multiple times his own weight. His mental circuitry grants him a bond with Steelheart, similar to the one with her brother, enabling him to be called upon by thought alone.