After the Skrull invasion, Tony Stark was stripped of his title of Director of S.H.I.E.L.D., as well as tossed out of the Avengers (which was disbanded). On the other hand, Norman Osborn (the former Green Goblin, and head of the Thunderbolts, was elevated to the U.S.'s top cop. His first act is to dismantle S.H.I.E.L.D. (renaming it H.A.M.M.E.R.) and rebuild the Avengers with his own hand-picked crew.
This new team of (Dark) Avengers consists of Ares, Sentry, Captain Marvel (the Kree warrior, Nov-Varr), Ms. Marvel (Moonstone), Wolverine (Wolverine's son, Daken), Hawkeye (Bullseye), Spider-Man (Venom/Scorpion,)and Iron Patriot (Osborn himself).