The Bane is the legion which Aedion Ashryver commands as general. Their camp resides in the Staghorn Mountains of Terrasen. In Heir of Fire, Aedion reveals that half the Bane are rebels and the other half are sympathizers, so many of their battles have been staged.
The Bane is notorious for its skill and brutality, and have worked in secret with rebel forces since Terrasen's downfall.
Empire of Storms
As of Empire of Storms, they are in Orynth, adding defenses to the city and preparing for war. Although Darrow states that the Lords of Terrasen now control the Bane (since the death of the King of Adarlan and Dorian releasing Terrasen from its rule), Aedion claims the Bane will only answer to Aelin Ashryver Galathynius.
When Aedion tells Lysandra that he is bisexual, it is revealed that a commander in his Bane is one of his former lovers. As of Empire of Storms, however, no members of the Bane have been officially introduced.