Navar Hef was a Sergeant of the Raven Guard during the Horus Heresy. A new recruit to the Raven Guard inducted after the Drop Site Massacre, Navar Hef was one of the first experimental Raptor warriors. Navar Hef suffered from the mutations that plagued the Raptors, growing physical claws. Nonetheless he remained loyal to Corax and fought bravely in the Battle of Ravendelve. Later, Hef was made a Lieutenant and led the surviving Raptors despite their mutations.
During the many years of fighting Horus from the shadows, the badly mutated Hef continued his war, seeking an end to his misery through death in combat. However at some point he came across Space Wolves forces under Arvan Woundweaver, which had been dispatched by Malcador the Sigillite to monitor Corax. After coming across the badly mutated Raptors, a crisis erupted between the two sides. Fearing they would be condemned to destruction and damn their Primarch with them, Navar Hef and his Raptors massacred the Space Wolves. He covered up the incident, but revealed his actions to Corax shortly before the Battle of Yarant. Seeking redemption by dying in Corax's last stand on Yarant, ultimately Navar Hef had his end once again denied when his Primarch refused to throw their lives away and evacuated the planet.