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 himself, 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 revealed amid the turmoil of the Firestorm Crisis, but it may be presumed the group is almost as ancient as Nod itself; with Kane selecting the outstanding personalities in the Brotherhood as his most trusted advisors or closest confidants among every generation of his 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 survived the aftermath of GDI's second military victory over the Brotherhood. At this time, the group appeared to be dominated by two personalities in particular: Anton Slavik (upper middle of the photo shown) and a general known as Marzaq (to the right of Slavik), both of whom attempted to establish total control and enforce their own concept of what Nod should become in the second interregnum.
The Inner Circle's members were all assassinated by CABAL's cyborgs, with only Anton Slavik successfully escaping the purge, as he relied on his own Black Hand forces for security, and not 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 Nod 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 an unnamed advisor. Kilian Qatar was supposedly a member as well, but she was framed by Abbess Alexa Kovacs and later executed by Kane.