The 2nd Eaglestrike core helmet, "Kerberos", is a direct reference to armor in the manga Kerberos Panzer Cop, which you might know as the movie Jin-Roh : r/halo
Jin Roh Helmet - Etsy
Interest - JIN ROH: The Wolf Brigade - Panzer Cop Armor (Protectgear) | RPF Costume and Prop Maker Community
Illang: The Wolf Brigade (2018) - New Mask Eyes Concepts | Brigade, Jin roh, Robot concept art
Jin-Roh Wolf Brigade custom head for 4" 6" 7" 12" action figures | eBay
Jin Roh helmet and mask WIP | Cosplay Amino
Jin Roh: the Wolf Brigade Panzer Cop Armor Files for 3D - Etsy
ArtStation - Illang: The Wolf Brigade (2018) - New Mask Eyes Concepts