For whatever reason (mostly writers being lazy and/or not checking consistency) multiple books are giving different Legion origins for the Hawk Lords. On one hand, their heraldry and use of Thunderhawks instead of Drop Pods do lean towards Raven Guard or Emperor's Children (who liked blowing the fuck out of the enemy with big-ass aircraft). On the other hand, they are a [[Codex Astartes|Codex compliant chapter]]. That and the fact that like other Ultramarine successor chapters ([[Aurora Chapter]] and [[Nemesis|Nemesis chapter]] for example) taking their names from their legion chapters, the 21st chapter of the Ultramarines Legion was known as The Hawks. But we don't know. They could be a [[Dark Angels]] chapter seeing as the call their air unit the Talon Wing. Thanks [[GeeDubs]].