The Inner Circle is a shadowy group embodying the highest echelon of power within the Brotherhood of Nod. Its secretive members are handpicked by Kane, and are second only to the Nod prophet in their authority over the Brotherhood.
Nothing is truly known about the Inner Circle prior to its existence being uncovered amid the turmoil of the Firestorm Crisis, but it may be presumed that the group is almost as ancient as Nod itself; with Kane selecting the outstanding personalities in the Brotherhood as his most trusted advisors and closest confidants among every generation of followers. Seth likely was one of its members during, and perhaps well before, the First Tiberium War.
Just prior to the events of the Firestorm Crisis, the Inner Circle was comprised of five Nod generals who had survived the aftermath of GDI's second military victory over the Brotherhood. At this time, the group appeared to be dominated by two powerful personalities in particular: the Black Hand's leader, Anton Slavik (upper middle of the photo shown), and a Nod general known as Marzaq (to the right of Slavik), both of whom attempted to establish total control over the Brotherhood, and enforce their own concept of what Nod should become in the second interregnum.
The Inner Circle's members in the era of the Second Tiberium War were all assassinated by CABAL's cyborgs at the commencement of the Firestorm Crisis, with only Anton Slavik escaping the purging, as he relied solely on his own Black Hand forces for his security--never on cyborg bodyguards.
Third Tiberium War
Following the return of Kane prior to the Third Tiberium War, the Inner Circle was reestablished as a secret collective of the prophet's most devoted and trusted loyalists. Three known members of the group during the era of the third conflict were Brother Eamonn, the Legendary Insurgent, and a mysterious unnamed advisor. General Kilian Qatar was supposedly a member of the Inner Circle as well, but was framed by Abbess Alexa Kovacs and later executed by Kane.