It emphasized "Battle Formations," which granted unique special rules for specific unit combinations, such as the Skyhammer Orbital Strike Force Unit Updates: This edition saw the introduction of the Centurion Devastator squads as staples in many competitive lists. www.wargamer.com How to Access Old Rulebooks
Librarians gained access to expanded psychic disciplines, significantly increasing their utility during the psychic phase. 7th Edition Space Marine Codex Pdf