The second Avengers omnibus continues the Silver Age run through the period when the team fully established its identity distinct from its founding members — the Cap's Kooky Quartet era, where Captain America led a team of reformed villains (Hawkeye, Scarlet Witch, Quicksilver) while the original Avengers stepped back. Stan Lee and then Roy Thomas built a book that proved the team concept could work without relying on its most popular members, a structural experiment that defined how Marvel managed ensemble casts going forward.